golang switch variable assignment

The switch statement in Golang

The switch statement is one of the most important control flow in programming. It improves on the if-else chain in some cases. Thus making it substantially easy to do the same task with much less code. In this post, we will see how we can use the switch statement in the Go programming language.

What is Golang Switch Statement?

The switch statement is a control flow mechanism by which a program can give control to different segments for different cases. It consists of the switch expression and the case blocks. Switches in Go can work with any type of variable as we will see.

The switch statement syntax

The syntax for the switch statement is relatively simple. We have to use the “switch” keyword to start the switch block then values and after that, the block can have multiple cases that will match the value. Below is the syntax for the switch-case.

The single-case switch statement

Switch-case in Go can have any number of case variables. Here is an example of a simple switch statement which only takes a single value to match. Later on, we will see that we can have as many as we want. So, here is the code for that.

The multi-case switch statement

In the case block, we can have multiple values. That means if any of the values match then the block executes. Here is an example showing a multi-case switch statement.

The “break” keyword

In the switch block, we can have the break keyword which will exit out of the entire block. The keyword has its own application. When we don’t want to run the case entirely we can simply use the break keyword. And that will allow us to exit from the block. Here is the break keyword in action.

The “fallthrough” keyword

Go has the fallthrough keyword which passes the execution to the next case. Now, sometimes we don’t want to go any further with the current case. We simply move on to the next one. The fallthrough keyword is just for that. The fallthrough keyword can be used as shown below.

The switch statement with the variable initializer

The switch statement in Go can declare the variable first then use it at the same time. This is an optional statement, which is pretty handy at times. Here is shown how to initialize the variable with the switch statement.

The switch statement with a predeclared variable

A variable declared before can be used in the switch statement as well. We can either check it at the time of the case declaration. Then we don’t need to put an expression after the switch keyword. Or, we can use that after the switch keyword and use it as a regular switch case. Examples of both are shown below.

The conditional case statement

Switches in Go can have conditions in the case. That means when the conditions match the block will execute. This is an example of using conditions in the cases.

The default case

The default case, as the name suggests is the block that will execute if none of the other values match. Here is an example using the default case.

Type-switches in Go

Go have type-switches , which allows using types instead of values in the switch statement. In the expression of the type-switch block, only interfaces can be used.

Golang Switch statement benefits

The switch statement can be used as a replacement for the if-else block. Sometimes it becomes verbose when we use the if-else block. At that point, the switch statement may be beneficial.

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In Go, the switch statement allows us to execute one code block among many alternatives.

The expression after the switch keyword is evaluated. If the result of the expression is equal to

• case 1 - code block 1 is executed
• case 2 - code block 2 is executed
• case 3 - code block 3 is executed

In case there is no match, the default code block is executed.

Note : We can also use if...else statements in place of switch . However, the syntax of the switch is much cleaner and easier to write.

Flowchart of Switch Statement

Example: switch case in Golang

In the above example, we have assigned 3 to the dayOfWeek variable. Now, the variable is compared with the value of each case statement.

Since the value matches with case 3 , the statement fmt.Println("Tuesday") inside the case is executed.

Note : Unlike other programming languages like C and Java, we don't need to use break after every case. This is because in Go, the switch statement terminates after the first matching case.

Go switch case with fallthrough

If we need to execute other cases after the matching case, we can use fallthrough inside the case statement. For example,

In the above example, the expression in switch matches case 3 so, Tuesday is printed. However, Wednesday is also printed even if the case doesn't match.

This is because we have used fallthrough inside case 3 .

• Go switch with multiple cases

We can also use multiple values inside a single case block. In such case, the case block is executed if the expression matches with one of the case values.

Let's see an example,

In the above example, we have used multiple values for each case:

• case "Saturday", "Sunday" - executes if dayOfWeek is either Saturday or Sunday
• case "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" - executes if dayOfWeek is either one of the value

Golang switch without expression

In Go, the expression in switch is optional. If we don't use the expression, the switch statement is true by default. For example,

In the above example, switch doesn't have an expression. Hence, the statement is true .

• Go switch optional statement

In Golang, we can also use an optional statement along with the expression. The statement and expression are separated by semicolons. For example,

In the above example, we have used the optional statement day := 4 along with the expression day . It matches case 4 and hence, Wednesday is printed.

Table of Contents

• Flowchart of switch Statement
• Example Go switch Case in Go
• Go switch Statement with fallthrough
• switch without expression

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Programming

5 switch statement patterns

Basic switch with default

No condition, fallthrough, exit with break, execution order.

• A switch statement runs the first case equal to the condition expression.
• The cases are evaluated from top to bottom, stopping when a case succeeds.
• If no case matches and there is a default case, its statements are executed.

Unlike C and Java, the case expressions do not need to be constants.

A switch without a condition is the same as switch true.

• A fallthrough statement transfers control to the next case.
• It may be used only as the final statement in a clause.

A break statement terminates execution of the innermost for , switch , or select statement.

If you need to break out of a surrounding loop, not the switch, you can put a label on the loop and break to that label. This example shows both uses.

• First the switch expression is evaluated once.
• the first one that equals the switch expression triggers execution of the statements of the associated case,
• the other cases are skipped.

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Core Go concepts: interfaces , structs , slices , maps , for loops , switch statements , packages .

Golang's Switch Case: A Technical Guide

• With Code Example
• January 16, 2024

Discover the incredible power of the switch statement in Golang – a game-changer in decision-making for your code. Unlike the sometimes clunky if-else statements, Go’s switch offers a cleaner and more straightforward way to handle conditions.

In this exploration of Golang switch case, we’ll break down the switch statement, using real-world examples to illustrate its efficiency. Say farewell to the complexities of if-else blocks and welcome a more concise syntax that turns your code into a masterpiece.

This journey isn’t just about making decisions – it’s about making them with finesse. Learn how the switch statement becomes your ally, providing an elegant solution for handling diverse scenarios in your code. It’s not just about control flow; it’s about enhancing your coding experience.

Join us as we navigate the world of Go, unveiling the secrets of the switch statement and empowering you to harness its capabilities. Your coding landscape is on the brink of transformation – are you ready to revolutionize your approach with the unparalleled simplicity and effectiveness of Go’s switch statement? Dive in and let your code do the talking.

Basic Golang Switch Case Statement

The basic syntax of the switch statement looks like this:

In the first example of golang switch case, the switch statement is used to check the value of the day variable. If day matches any of the cases, the corresponding block of code is executed. If none of the cases match, the code inside the default block is executed.

In the second example, the switch statement is used without an expression. Instead, it checks conditions within each case. The first case that evaluates to true executes its corresponding block. If no condition is true , the code inside the default block (if present) is executed.

Fallthrough in Switch

Go’s switch statement does not automatically fall through to the next case. However, you can explicitly use the fallthrough keyword to achieve this behavior:

In this example, when number is 2 , the fallthrough keyword is used after the Two case. This causes the execution to fall through to the next case ( Three ). Without the fallthrough statement, the switch statement would exit after executing the matching case.

Type Switch

Go’s switch statement can also be used for type-switching. It allows you to check the type of an interface variable:

In this example of golang switch case, the checkType function uses a type switch to determine the type of the argument x . The case statements check if x is an int or a string , and the default case handles any other type.

The switch statement in Go is a versatile tool for making decisions based on the value or type of an expression. Whether you’re comparing values, handling multiple conditions, or checking types, the switch statement provides a clean and efficient syntax for expressing decision logic.

Choosing Between switch and if-else in Go

The choice between using a switch statement and a series of if-else statements in Go depends on the specific requirements and readability of the code. Both constructs are used for making decisions based on conditions, but they have different use cases and characteristics.

switch Statement:

Clear and Concise for Multiple Conditions:

• switch is particularly suitable when there are multiple conditions to check against a single value.
• It provides a clean and concise syntax, especially when comparing a value against multiple possible values.

Easier to Read and Maintain:

• switch statements are often easier to read and maintain when there are several possible cases.
• The structure of a switch statement can make the code more organized and comprehensible.

Type Switching:

• switch statements can be used for type-switching when checking the type of an interface variable.

Fallthrough:

• switch allows the use of fallthrough to execute the next case after a match. This can be useful in certain scenarios.

Example of a switch statement:

if-else Statements:

Flexible Conditions:

• if-else statements are more flexible when dealing with complex conditions that might not fit well in a switch .
• They are suitable for scenarios where conditions are more dynamic or involve multiple variables.

Readable for Few Conditions:

• For a small number of conditions or a simple binary decision, if-else statements can be more readable.

Comparisons and Range Checks:

• if-else statements are suitable for range checks, mathematical comparisons, and boolean conditions.

Example of if-else statements:

When to Use Each:

Opt for switch in the Following Scenarios:

• When dealing with multiple conditions for a single value.
• In situations where the code requires checking against numerous possible values.
• When type-switching becomes necessary.

Choose if-else under the Following Circumstances:

• When conditions are dynamic and may involve multiple variables.
• If there are only a few conditions to check.
• When conditions involve complex boolean expressions.

Considerations:

Readability:

• Consider the readability and clarity of the code. Choose the construct that makes the code more understandable for future readers.

Code Style:

• Follow the code style of your team or project. Consistency in code style enhances collaboration.

Specific Requirements:

• Choose the construct that best fits the specific requirements of the decision logic.

To wrap it up, when navigating the diverse landscape of decision-making in your code, both switch and if-else statements offer unique strengths. The selection between them hinges on the intricacy of your conditions and your code’s readability objectives. Opt for the switch statement when aiming for clarity and conciseness with value-based conditions. On the flip side, embrace the flexibility of if-else when dealing with more intricate or adaptable conditions.

Have thoughts to share on your preference or experiences with these constructs? We’d love to hear from you! Drop a comment below and let’s continue the conversation. Your insights could be the key to helping fellow developers make informed decisions in their coding journeys.

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last modified April 11, 2024

In this article we show how to work with switch statement in Golang.

We use Go version 1.22.2.

Go switch statement

Go switch statement provides a multi-way execution. An expression or type specifier is compared to the cases inside the switch to determine which branch to execute. Unlike in other languages such as C, Java, or PHP, each case is terminated by an implicit break; therefore, we do not have to write it explicitly.

Switch cases evaluate cases from top to bottom, stopping when a case succeeds. Switch statements work on values of any type, not just integers.

There are two types of switch statements: switch expressions and switch types. We can use commas to separate multiple expressions in the same case statement. The switch without an expression is an alternate way to express if/else logic.

The default statement can be used for a branch that is executed, when no other cases fit. The default statement is optional.

Go switch example

The following is a simple example of a switch statement in Go.

In the code example, we find out the current weekday and print the corresponding message.

The switch statement takes an expresssion, which evaluates to the current weekday.

If the weekday evaluates to time.Monday , we print the "Today is Monday" message.

Go switch multiple expressions

It is possible to place multiple expressions in one case.

The example prints either weekday or weekend, depending on the evaluation of multiple expressions in two case statements.

Go switch default

The default statement can be used for all the values that do not fit the specified cases.

The example checks the sizes of clothes. If a value that is not recognized is used, it prints "unknown" to the terminal.

Go switch optional statement

An optional initializer statement may precede a switch expression. The initializer and the expression are separated by semicolon.

In the code example, we have both the switch initializer and the expression. The switch statement determines if the value is even or odd.

The num := 6 is the switch initializer and the num % 2 is the switch expression.

Go switch break statement

Go uses an implicit break statement for each case. This is different from languages like C or Java, where the break is necessary. We can also explicitly specify break when needed.

In the code example, we loop through a string which contains white spaces. Only non-white spaces are printed.

We have a space a tab and a new line white space characters in the string.

We go through the string elements with for range loop.

If we encounter the specified three white spaces, we terminate the switch statement with break .

Go switch without expression

When used without an expression, the switch statement is effectively equal to switch true . This form can be used instead of multiline if/else statements to shorten code.

Depending on the current hour, the example prints AM or PM .

Go switch fallthrough

We can use the fallthrough keyword to go to the next case.

Imagine that we go from A stop to E stop. We determine how many stops are ahead of us, basend on the next visible stop.

Go type switch

With a type switch we can switch on the type of an interface value.

In the code example, we print the data type of a value.

For the bool type, we print "boolean".

The 112523652346.23463246345 value is a float64 .

The Go Programming Language Specification

In this article we have covered the switch statement in Golang.

My name is Jan Bodnar and I am a passionate programmer with many years of programming experience. I have been writing programming articles since 2007. So far, I have written over 1400 articles and 8 e-books. I have over eight years of experience in teaching programming.

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Golang Switch Statements (A Complete Guide)

What is switch statement in go.

The switch statement in Go is a control flow statement that is used to execute a block of code among many alternatives. Switch statements are declared using the switch keyword followed by the condition to be evaluated. The condition can be a variable, constant, or expression.

The switch statement is similar to the if-else statement. The difference is that the switch statement can have multiple cases. The switch statement is also known as the switch-case statement.

Syntax of Switch Statement in Go

The syntax of the switch statement in Go is as follows:

The switch statement is followed by the case keyword. The case keyword is followed by the value to be compared with the condition. The case keyword is followed by the code block to be executed if the condition is equal to the value. The default keyword is used to execute a block of code if none of the cases is true.

Example of Switch Statement in Go

The following example shows the use of the switch statement in Go:

The output of the above program is:

Switch Statement with Multiple Cases

The switch statement can have multiple cases, you can have as many cases as you want. The following example shows the use of the switch statement with multiple cases:

Switch Statement with Fallthrough

Fallthrough is a keyword that is used to execute the next case in a switch statement. The fallthrough keyword is used to execute the next case even if the condition is not true. The following example shows the use of the fallthrough keyword:

In the above example, case 10 is executed and then the fallthrough keyword is used to execute the next case which is case 20.

golang switch case break

The break keyword is used to terminate the switch statement when a given condition is true.

The following example shows the use of the break keyword:

Nothing is printed because the switch statement is terminated after the break keyword.

golang switch channel

A channel is a communication mechanism that allows one goroutine to pass values of a specified type to another goroutine.

The following example shows the use of the switch statement with a channel:

In the above example, the select statement is used to receive the values from the channel. The select statement is used to receive the values from the channel. The select statement is used to receive the values from the channel.

Switch Statement with Multiple Conditions

The switch statement can have multiple conditions using the || , && , and ! operators. The following example shows the use of the switch statement with multiple conditions:

In the above example, the switch statement is used to check if the num variable is equal to 10 and the x variable is equal to 20.

Switch Statement with Type Switch

The switch statement can be used to check the type of a variable using the type keyword. By combining type and := we can create a type switch guard . The following example shows the use of the switch statement with the type keyword:

if we change the value of the x variable to 10 the output will be:

• The switch statement is used to execute a block of code based on the value of a variable.
• The switch statement can have multiple cases, you can have as many cases as you want.
• The switch statement can have multiple conditions using the || , && , and ! operators.
• The switch statement can be used to check the type of a variable using the type keyword.

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Go by Example : Switch

Next example: Arrays .

by Mark McGranaghan and Eli Bendersky | source | license

The switch statement lets you check multiple cases. You can see this as an alternative to a list of if-statements that looks like spaghetti. A switch statement provides a clean and readable way to evaluate cases.

While the switch statement is not unique to Go, in this article you will learn about the switch statement forms in golang.

The basic syntax of a switch statement is:

You can also check conditions:

The second form of a switch statement is not to provide any determined value (which is actually defaulted to be true).

Instead it test different conditions in each case branch. So what is a condition?

A condition can be x > 10 or x == 8 .

The code of the branch is executed when the test result of either branch is true.

The third form of a switch statement is to include an initialization statement:

Variable var1 can be any type, and val1 and val2 can be any value of the same type.

The type is not limited to a constant or integer, but must be the same type; The front braces {must be on the same line as the switch keyword.

You can test multiple potentially eligible values at the same time, using commas to split them, for example: case val1, val2, val3: .

Note Once a branch has been successfully matched, the entire switch code block is exited after the corresponding code is executed, that is, you do not need to use the break statement specifically to indicate an end.

If you want to continue with the code for subsequent branches after you finish the code for each branch, you can use the fallthrough keyword to achieve the purpose.

The example below demonstrates the use of a switch statement in Go.

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Golang Switch

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Table of Contents

Introduction

Understanding the golang switch statement, golang switch with multiple expressions, tips, tricks, and common pitfalls.

• The GoLang Switch statement starts with the keyword "switch" followed by an expression (which can be optional), and a series of cases.
• The expression is compared with the values of each case. If there's a match, the corresponding block of code is executed.
• Unlike other languages, GoLang does not require a "break" statement at the end of each case, because an automatic break is provided at the end of each case. This is a unique feature of GoLang that helps prevent fallthrough errors, a common pitfall in languages like C or Java.
• In GoLang, you can include multiple expressions in a case statement, separated by commas. This makes it more flexible to handle complex conditions.
• Be mindful of the 'fallthrough' keyword: In GoLang, the switch cases do not fallthrough by default. However, you can use the 'fallthrough' keyword to achieve this. But, it can also lead to errors if not used properly.
• Remember the default case: The default case is executed when no other case matches. It's always good practice to include a default case in your switch statement to handle unexpected values.
• Switch without an expression: In GoLang, you can use a switch statement without an expression. This can act like a cleaner alternative to long if-else chains.

Go Switch - 6 ways of using Switch in Go

• August 17, 2021
• Web Development

6 ways of using Switch statement in Go

Basic switch.

Switch case is commonly used there are multiple condition checks to be done for a particular variable. It is easier to understand than having multiple if statements in your code.

Switch statement evaluates the expression and executes the block of code that matches from the list of possible choices

In the above program, we have a status variable that can correspond to different values based on its integer value. Business logic suggests the following

1 - In progress

Using the switch statement, we can check the value of the status and print the corresponding value.

Switch with default statement

There are instances when the expression being evaluated will contain a value not present in the list of cases defined. default statement comes to our rescue by executing that case if there is no match with the other case defined.

Switch without condition

Switch statement supports expression less statement when defining. If you just want multiple condition to be check and give those condition in the case, you can remove the expression in the switch statement

Switch with case list

Another common use case will be to have multiple expressions in a case. Multiple expressions are separated by commas.

Switch with fallthrough statement

Execution of the statements in switch goes from top to bottom. When a particular case evaluates to be true, execution of the statement takes place. Control jumps out of the switch after execution of the successful case. fallthrough statement is used to transfer the execution of the code to the first statement of the case after the executed case

Fallthrough can be used when you want to execute the successive case irrespective of its condition

Status is done Status is done but has some issues

Things to note about fallthrough

• Fallthrough execute the next case even if the case will evaluate to false. Above example shows that the last case is executed but the condition status > 6 is false.
• Fallthrough has to be the last statement in your case
• Fallthrough cannot be present in the last case

Switch with break statement

Execution of the case statements can be stopped by using the break statement.

Status is done

In the above program, when the status is 2 , then the second case gets executed. if condition becomes true and so break is called which sends the control to the end of the switch statement without running the fallthrough statement

Similarly, you can break from a labeled loop by specifying the label after the break statement

for loop without a condition will execute infinite loop until it runs into a break statement. For more info you can have a loop into this blog post.

https://www.eternaldev.com/blog/go-learning-for-loop-statement-in-depth/

status variable will contain a random value between 0 to 5 for each loop iteration. If that value is less than 3, “Waiting for status to complete” is printed. If the value is greater than or equal to 3, “Status is done” is printed and we break the outer for loop.

So this program executes until we get values from 3 to 5 from the random value function.

Practical Assignment - Try these out

Simple app which takes the name of the task and status of the task from the user, and outputs the remaining status for the task using the Switch statement

• Status list - Created, Sprint Ready, Work in Progress, Completed, Deployed, Verified
• User input - “Feature A”, “Work in Progress” - Output - 3 steps are pending
• User input - “Feature C”, “Created” - Output - 5 steps are pending

Use the live code editor below to work on the assignment

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The Go extension allows you to launch or attach to Go programs for debugging. You can inspect variables and stacks, set breakpoints, and do other debugging activities using VS Code’s Debugging UI .

These debugging features are possible by using Delve , the Go debugger.

Previously, the Go extension communicated with Delve through a custom debug adaptor program ( legacy mode). Since Delve 's native debug adapter implementation is available, the Go extension is transitioning to deprecate the legacy debug adapter in favor of direct communication with Delve via DAP .

📣 We are happy to announce that the new dlv-dap mode of Delve integration is enabled for local debugging by default. For remote debugging it is the default in Go Nightly and is available with stable builds on demand with "debugAdapter": "dlv-dap" attribute in launch.json or settings.json !

Many features and settings described in this document may be available only with the new dlv-dap mode. For troubleshooting and configuring the legacy debug adapter, see the legacy debug adapter documentation .

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To learn more about debugging in Go, watch Go: Writing and debugging fast, reliable, and efficient software .

Review the Features section for an overview of the Go Extension's debug UI and available features.

Stay up to date

Delve’s native DAP implementation is under active development. Take advantage of the most recent features and bug fixes by installing the latest version of dlv using the Go:Install/Update Tools command from the Command Palette (Linux/Windows: Ctrl + Shift + P , Mac: Command + Shift + P ). The command will show dlv in the tool list.

Once dlv is installed on your system, the extension will prompt you for update whenever installing a newer version is necessary. You can set the go.toolsManagement.autoUpdate setting so the extension can update dlv automatically for you.

If you need to install dlv manually outside of VS Code, follow the instruction in Manually installing dlv . An example of a situation where manual installation might be needed is if you are building a dev container with the necessary tools preinstalled, or installing dlv built from the tree head.

Switch to legacy debug adapter

Note: The extension still uses the legacy debug adapter for remote debugging.

If you need to use the legacy debug adapter for local debugging ( legacy mode) by default, add the following in your VSCode settings.

When mode is set to remote you must explicitly set debugAdapter to dlv-dap to override the legacy adapter default.

If you want to switch to legacy for only a subset of your launch configurations, you can use the debugAdapter attribute to switch between "dlv-dap" and "legacy" mode.

If you chose to switch to legacy because of bugs or limitations in the new debug adapter, open an issue to help us improve.

For general debugging features such as inspecting variables, setting breakpoints, and other activities that aren't language-dependent, review VS Code debugging .

When you need more than the default debugging setup, you can create a launch configuration file for the project.

To create a configuration file:

• In the the Run view , click "create a launch.json file"
• Choose Go: Launch Package from the debug configuration drop-down menu. VS Code will create a launch.json file in a .vscode folder in your workspace (project root folder) or in your user settings or workspace settings .

If you already have a launch.json for your project, you can open it using the Command Palette Open launch.json command.

To add a new configuration to an existing launch.json file:

• Open your launch.json file using the Command Palette Open launch.json command.
• Click the Add Configuration button to invoke the snippet IntelliSense.

There are many configuration attributes (see the Launch.json attributes section). IntelliSense in VS Code’s launch.json editor will help you navigate available options and documentation.

To launch and debug your project, select Run > Start Debugging (F5) .

The launch feature uses a launch request type configuration in your launch.json file. Its program attribute needs to be the absolute path to either the Go file, or folder containing the main package or test file. In this mode, the Go extension will start the debug session by building and launching the program. The launched program will be terminated when the debug session ends.

• debug : build and debug a main package
• test : build and debug a test
• The binary must be built with go build -gcflags=all="-N -l" to disable inlining and optimizations that can interfere with debugging.
• auto : automatically choose between debug and test depending on the open file

⚠️ For "Remote Debugging" , add the port attribute to the launch configuration. VS Code will connect to the external user-specified dlv dap server at host:port and launch the target there.

For remote debugging, the program attribute must point to the absolute path to the package or binary to debug in the remote host’s file system even when substitutePath is specified.

You can use this configuration to attach to a running process or a running debug session.

• remote : attaches to an in-progress debug session run by an external server.

You can debug an already running program using the local mode type configuration. The Go extension will start dlv dap and configure it to attach to the specified process. Users can select the process to debug with one of the following options:

• Specifying the numeric process id (PID) with the processId attribute.
• Specifying the target program name in the processId attribute. If there are multiple processes matching the specified program name, the extension will show the list of matching processes at the start of the debug session.
• Specifying 0 in the processId attribute and selecting the process from the drop-down menu at the start of the debug session.

NOTE: For remote debugging, add the port attribute to the launch configuration. VS Code will connect to the external user-specified dlv dap server at host:port and attach to the target there.See "remote debugging" for more details).

You can connect to an already running remote debug session using the remote mode. Specify optional host and required port for the external dlv --headless server that already took program or process id details as command-line arguments. See "Remote Debugging" for more details).

When you end an attach debug session, the debug UI allows you to choose to:

• local : leave the target process running (dlv terminates).
• dlv debug/test/exec : terminate the target process if dlv terminates.
• dlv attach : leave the target process running even if dlv terminates.
• Stop: stop the attached server and the target process.

Debug actions

Once a debug session starts, the Debug toolbar will appear on the top of the editor.

The available commands are:

• Continue / Pause F5
• Step Over (aka next in Delve) F10
• Step Into (aka step in Delve) F11
• Step Out (aka stepout in Delve) Shift+F11 or ⇧F11
• Restart (currently this is "Stop + Start") Ctrl+Shift+F5 or ⇧⌘F5
• Stop (terminate the debugee. Available in Launch request) Shift+F5 or ⇧F5
• Disconnect (detach from the debugee. Available only in Attach request) Shift+F5 or ⇧F5
• Terminate (terminate the debugee. Available only in Attach request) Alt+Shift+F5 or ⌥⇧F5

Breakpoints

See VS Code’s Debug Documentation on Breakpoints to get familiar with VS Code’s UI. The Go debugger supports multiple ways to configure breakpoints.

• Breakpoints : you can set breakpoints by clicking on the editor margin or using F9 on the current line. If the breakpoints can’t be set by Delve, VS Code will show the failure reason and grey out the dot.

• Expression condition: takes a boolean expression.
• Hit count: supports comparison operators ( > , >= , < , <= , == , != ) with an integer value. % n form means we should stop at the breakpoint when the hitcount is a multiple of n .
• Function Breakpoints : breakpoints can be set based on function names. Press the + button in the BREAKPOINTS section header and enter the location in the form of <function>[:<line>] . This sets the breakpoint in the line inside the function . The full syntax for function is <package>.(*<receiver type>).<function_name> as specified in Delve’s location spec . Function breakpoints are shown with a red triangle in the BREAKPOINTS section.
• Logpoints : a logpoint is a variant of breakpoint that does not 'break', but instead logs a message to DEBUG CONSOLE and continues execution. Expressions within {} are interpolated. For the list of acceptable expressions and syntax, see Delve's documentation .

Data inspection

You can inspect variables in the VARIABLES section of the Run view or by hovering over their source in the editor. Variable values and expression evaluation are relative to the selected stack frame in the CALL section.

By default, the VARIABLES section hides global variables, and shows only local variables and function arguments. However, you can still inspect global variables from the DEBUG CONSOLE panel. If you prefer to have the VARIABLES section show global variables, set the showGlobalVariables attribute in the launch.json configuration, or set it in the go.delveConfig setting.

When you select a variable and right click from the VARIABLES section, the context menu will present shortcuts to features such as:

• Set Value : you can set/modify simple string, numeric, pointer values. Using composite literals, or memory allocation is not supported.
• Copy Value : this copies the value in clipboard.
• Copy as Expression : this is useful when you need to query from the REPL in the DEBUG CONSOLE panel.
• Add to Watch : this will automatically add the expression to the WATCH section.

Shadowed variables will be marked with () .

⚠️ Delve debugger imposes variable loading limits to prevent loading too many variables at once and negatively impacting debugging latency. The dlv-dap mode uses a different approach. It takes advantage of the interactive UI features to provide on-demand loading of individual variables, paging of arrays, slices and maps and increased string limits depending on the context. We continue to explore additional interactive features to balance performance and usability of variable loading and look forward to your feedback.

You can inspect variables and evaluate expressions from the DEBUG CONSOLE panel too. Acceptable expressions are either

• A valid Delve expression , or
• call <function_call_expression> to call functions.

Variables and expressions accepted in DEBUG CONSOLE can be also registered in the Run view’s WATCH section, so they can be evaluated automatically as you debug. The "Add to Watch" feature from the VARIABLES section is convenient when you want to register interesting variables.

⚠️ Function call feature is highly EXPERIMENTAL due to the limitation in Go runtime. Registering function calls in the WATCH section can often be problematic. Pause, stop, and disconnect will not work while a function call is running.

Hover over variables in editors during debugging shows the value of the variable. For this feature, VS Code extracts the variable expression and makes a request to the debugger to evaluate the expression. Delve evaluates the expression relative to the highlighted stack frame chosen in the CALL STACK. By default, that is the current top-most frame.

⚠️ Limitation

• VS Code heuristically determines the variable expression without full understanding of the scope & the currently selected frame. Delve tries to evaluate the provided expression in the selected frame. As a result, hover over variables outside the selected frame’s function may present incorrect information.

You can inspect all goroutines and their stacks in the CALL STACK section. The CALL STACK section UI allows switching between goroutines or selecting a different stack frame. As a different stack frame or different goroutine is selected, the scope shown in the VARIABLE section will be updated for the newly selected stack frame, and the expressions in the WATCH section will be automatically reevaluated relative to the newly selected stack frame.

• Goroutine stacks are annotated with their internal goroutine IDs.
• The current goroutine is marked with * . If multiple goroutines stop (e.g. hit breakpoints) concurrently, Delve will pick one randomly. There also might not be a current goroutine (e.g. deadlock, pause or internal breakpoint hit by a system thread not running a goroutine).
• If you click a goroutine call stack from the CALL STACK section, the goroutine is selected .
• You can select a frame of the selected goroutine. The VARIABLE and WATCH sections will be updated accordingly and the cursor in the editor will be moved to the corresponding location in the source code.
• Runtime stack frames are deemphasized (greyed out or collapsed).
• Thread IDs are shown for scheduled goroutines.
• Stop reason. It’s possible that there are multiple reasons goroutines were stopped, but currently only one reason is presented.
• File name and line number of the frame.
• You can trigger a debug action with the selected goroutine. Note: Resuming or stopping only a single goroutine (Go Issue 25578 , 31132 ) is currently not supported, so the action will cause all the goroutines to get activated or paused.
• Function name of the frame.

When the program stops due to exception, panic, or bad access error, the CALL STACK shows the stop reason and the editor highlights the source location with more details.

dlv command from DEBUG CONSOLE

DEBUG CONSOLE accepts commands that allow users to dynamically inspect/change debug configuration, or inspect the list of source code compiled in the debugged binary. Use dlv help and dlv config -list from the DEBUG CONSOLE panel to see the list of supported commands and dynamically adjustable settings.

Configuration

Launch.json attributes.

There are many attributes that you can adjust in the launch and attach debug configuration. The following general attributes are mandatory for all launch configurations.

• name : the name of your configuration as it appears in the drop-down in the Run view.
• type : the debugging type VS Code uses to decide which debugging extension should be used. Always leave this set to "go" .
• request : launch or attach .

Here is the list of attributes specific to Go debugging.

⚠️ Delve resolves relative paths from dlv dap process's working directory, but from which directory the extension spawns the dlv dap process is an implementation detail. Thus, use the VS Code variables substitution to ensure consistent expansion of paths. VS Code will resolve the variables inside strings in launch.json before passing the configuration to the Go extension and dlv dap . For example, ${workspaceFolder} will be replaced with the absolute path to the workspace root folder. When appropriate, the Go extension will resolve relative paths or home directory (~) before sending the configuration to dlv dap .

Debug symlink directories

Since the debugger and go compiler use the actual filenames, extra configuration is required to debug symlinked directories. Use the substitutePath property to tell the debugAdapter how to properly translate the paths. For example, if your project lives in /path/to/actual/helloWorld , but the project is open in vscode under the linked folder /link/to/helloWorld , you can add the following to your config to set breakpoints in the files in /link/to/helloWorld :

You can adjust the default value of the following configuration properties using go.delveConfig settings. These default values are useful when you choose to run a debug session without the launch configuration set in launch.json . For example, debug sessions started using the Debug Test code lenses use the adjusted values from these settings.

• debugAdapter : Controls which debug adapter to use (default: legacy ). Select ‘dlv-dap’.
• showGlobalVariables : Show global variables in the Debug view (default: false ).
• substitutePath : Path mappings to apply to get from a path in the editor to a path in the compiled program (default: [] ).

⚠️ Where is the dlvLoadConfig setting? Delve debugger imposes variable loading limits to avoid loading too many variables at once and negatively impacting debugging latency. The legacy adapter supported dlvLoadConfig to adjust these limits for the duration of the session. The user therefore had to come up with a one-size-fits-all limit if the default behavior was not satisfactory. dlv-dap mode uses a different approach as described in the Data Inspection section . If this setting is configured and dlv-dap mode is used, the extension will show a warning prompt now. If the current variable loading behavior and internal limits are not working for you, please open an issue and share your feedback.

Advanced topics

Go debug extension architecture overview.

VS Code implements a generic, language-agnostic debugger UI based on Debug Adapter Protocol (DAP), an abstract protocol for communicating with debugger backend. Previously, the Go extension used an intermediary typescript program (legacy debug adapter) to launch Delve and adapt Delve to DAP. With the new, native DAP implementation in Delve , the intermediary program is no longer necessary, and efficient and tight integration with Delve becomes possible.

For information on debugging using the legacy debug adapter, please see the old Debugging Documentation . Note that many new or enhanced features discussed in this document may not be available with the legacy debug adapter.

Handling STDIN

The Go extension and dlv started as a subprocess of the extension do not have access to tty . The Go extension captures and forwards STDOUT/STDERR of the debug program to VS Code, so they can appear in DEBUG OUTPUT panel. But this arrangement does not handle STDIN.

When the target program needs to read from STDIN or access terminals ( tty ), use the "console" launch option that controls where the dlv debugger and the target process run:

• integratedTerminal for the terminal inside VS Code
• externalTerminal for the terminal outside VS Code

The Go extension delegates interaction with terminals to VS Code using Debug Adapter Protocol's RunInTerminal functionality . For configuring VS Code's terminal related behavior, see VS Code's documentation .

Debug programs and tests as root

In order to run and debug a program or a package test running as root, the debugger ( dlv ) must run with root privilege, too. You can start the debug session with root privilege utilizing the "asRoot" AND "console" launch options. This is currently supported only on Linux and Mac.

When asRoot is true, the Go extension will use the sudo command to run dlv . Since sudo may ask you to enter password, the debug session needs terminal access so set "console": "integratedTerminal" or "console": "externalTerminal" in the launch configuration.

Debug a program as root

For example, the following launch configuration will start myprogram and debug it by running sudo dlv dap command in the integrated terminal.

The asRoot setting can be used with auto / test / debug launch modes that build the target binary to debug. That means the go command will be invoked as root to compile the binary, too. This can cause issues:

• by default, sudo does not preserve the user's current environment variables (see documentations about sudo's --preserve-env option). For example, PATH or library paths required for build may be different.
• Go environment variable settings usually associated in the home directory are different.
• Module/build caches used during build as root may be different from the caches used in your normal build. If they are the same, you may encounter permission errors due to cache data written to the caches as root.

Instead, you can arrange the exec launch mode to work with a pre-launch task .

First, configure a debug build task to compile the target binary.

In .vscode/tasks.json :

The -gcflags=all=-N -l flag tells the go build command to preserve the debug information. The -o flag causes the compiled binary to be placed in "${fileDirname}/__debug_bin" . Extra build flags and environment variables used for build should be configured here as args or options 's env settings.

It might be useful to add __debug_bin to your .gitignore to avoid debugging binaries getting checked-in into your repository.

Then, configure the launch config to run the task before starting debugging.

In .vscode/launch.json :

Settings ( args , cwd , env , ...) configured in the above launch.json will only apply when running the compiled binary, not when building the binary.

Debug a package test as root

To debug package tests as root add the following launch and task configurations.

Manually install dlv

On rare occasions, you may want to install dlv by yourself instead of letting the extension handle its installation.

First, find where the Go extension finds tools. Like other tools the extension uses , the Go extension searches the dlv executable from ${GOPATH}/bin , ${GOBIN} and ${PATH} (or Path in Windows). So, install dlv in the directory. The easiest way to check the tool installation location the Go extension uses is currently by running the Go: Locate Configured Go Tools command from the command palette (⇧+⌘+P or Ctrl+Shift+P).

If your Go version is 1.16 or newer:

If your Go version is older than 1.16:

You can choose to install a different version of dlv by specifying a specific commit hash, a branch name (e.g. master ), or a released version instead of latest . For more details about manual installation, see Delve's documentation .

If you want to explicitly specify the location of the delve binary, use the go.alternateTools setting:

Remote debugging

If you are able to use the Remote Development extensions and VS Code’s universal remote development capabilities , that is the recommended way to debug Go programs remotely. Check out Getting started section and Remote tutorials to learn more.

Remote debugging is the debug mode commonly used to work with a debugger and target running on a remote machine or a container. In spite of its name, it can also be used on a local machine with server started in an external terminal (e.g. to support entering stdin into the server's terminal window).

With the introduction of dlv dap users now have two options for remote (i.e. external) debugging.

Connect to headless delve with target specified at server start-up

In this mode the user must first manually start a dlv --headless server listening at host:port while specifying the target program to debug/test/exec or a process to attach to on the command-line. A remote attach configuration is then used to connect to the debugger with a running target.

The headless dlv server can now be used with both "debugAdapter": "legacy" (default value) and "debugAdapter": "dlv-dap" (with Delve v1.7.3 or newer) as well as Delve's command-line interface via dlv connect . The --accept-multiclient flag makes this a multi-use server that persists on Disconnect from a client and allows repeated connections from any of the aforementioned clients. A combination of --accept-multiclient --continue flags can be used to resume process execution on start-up. Please see dlv --help and dlv [command] --help for dlv's command-line options.

We encourage you to give the newly added "debugAdapter": "dlv-dap" support a try and to let us know of any issues . If you need to use the legacy mode, pleasse also see the legacy remote debugging documentation.

For example, start external headless server:

Connect to it with a remote attach configuration in your launch.json :

Connect to delve dap with target specified at client start-up

In this mode the user must first manually start a dlv dap server listening at host:port and then specify the target program via launch or attach client config with a "port" attribute. Instead of starting a new local server, the Go extension will tell VS Code to connect to the server specified by host:port attributes and then send a request with the target to debug. This option provides the flexibility of easily adapting local configurations to connect to external servers, but ⚠️ must be used with care since anyone who can connect to the server can make it run arbitrary programs.

When using launch mode, the program attribute must point to the absolute path of the package or binary to debug in the remote host’s file system even when substitutePath is specified. When using attach mode outside of local host, you need to specify the processId in the config since the processId resolution feature cannot gather information about processes running remotely.

Start a dlv dap server ready to accept a client request to launch or attach to a target process:

Use the following launch configuration to tell dlv to execute a binary precompiled with go build -gcflags=all="-N -l" :

Or have the binary compiled by dlv dap by modifying the above configuration to use:

⚠️ Limitations

• Unlike dlv --headless above, dlv dap does not support --accept-multiclient or --continue flags, which means after a debug session ends, the dlv dap process will always exit.
• If you use debug or test mode launch requests, Delve builds the target binary. Delve tries to build the target from the directory where the dlv process is running, so make sure to run the dlv command from the directory you would run the go build or go test command.

Run debugee externally

Sometimes you might like to launch the program for debugging outside of VS Code (e.g. as a workaround of the missing console support to enter stdin via an external terminal or separate target's output from debug session logging). There are currently two options:

• Compile and run the target program from the external terminal and use the "attach" configuration .
• Run the debug server from the external terminal with --listen=:<port> and have VS Code connect to it using port in your launch configuration (see "Remote Debugging" for more details)

Troubleshooting

The suggestions below are intended to help you troubleshoot any problems you encounter. If you are unable to resolve the issue, please take a look at the current known debugging issues or report a new issue .

• Read documentation and FAQs . Also check the Delve FAQ in case the problem is mentioned there.
• Check your launch.json configuration. Often error messages appearing in the DEBUG CONSOLE panel reveal issues.
• Update Delve ( dlv ) to pick up most recent bug fixes. Follow the instruction .
• Check if you can reproduce the issue with dlv , the command line tool from the integrated terminal. If it's reproducible when using dlv , take a look at the Delve project issue tracker .
• Capture logs and inspect them.
• Look at the existing debugging issues if similar issues were reported.
• If none of these solve your problem, please open a new issue .

I need to view large strings. How can I do that if dlvLoadConfig with maxStringLen is deprecated?

The legacy adapter used dlvLoadConfig as one-time session-wide setting to override dlv's conservative default variable loading limits, intended to protect tool's performance. The new debug adapter is taking a different approach with on-demand loading of composite data and updated string limits, relaxed when interacting with individual strings. In particular, if the new default limit of 512, applied to all string values in the variables pane, is not sufficient, you can take advantage of a larger limit of 4096 with one of the following:

• Hover over the variable in the source code
• Copy as Expression to query the string via REPL in the DEBUG CONSOLE panel
• Copy Value to clipboard

Please open an issue if this is not sufficient for your use case or if you have any additional feedback.

Why does my debug session have an invalid command error when I try to step?

When stepping through a program on a particular goroutine, the debugger will make sure that the step is completed, even when interrupted by events on a different goroutine. If a breakpoint is hit on a different goroutine, the debug adapter will stop the program execution to allow you to inspect the state, even though the step request is still active.

If you attempt to make another step request you will get an invalid command error.

Use Continue to resume program execution.

If you do not want the step request to be interrupted, you can disable all breakpoints from VS Code from the context menu in the Breakpoints view.

My program does not stop at breakpoints

Check the "BREAKPOINTS" section in the debug view and see if the breakpoints are greyed out when your debug session is active. Setting stopOnEntry is a great way to pause execution at the start to verify breakpoints are set correctly. Or enable logging and see if setBreakpoints requests succeeded with all the breakpoints verified .

This problem often occurs when the source location used in compiling the debugged program and the workspace directory VS Code uses are different. Common culprits are remote debugging where the program is built in the remote location, use of symbolic links, or use of -trimpath build flags. In this case, configure the substitutePath attribute in your launch configuration.

Trimpath tips

If you are using -trimpath to build your program, you need to add entries to substitute path to let the debugger know how to map the package paths that are compiled in the binary to the files that you are looking at in the editor.

Here are some tips for configuring substitutePath. This assumes that your program is using module mode, which is the default.

One rule that you will need will map your main module. The mapping will map "from" the file path to the directory containing the module, "to" the module path.

You will also need to create a similar mapping for all dependencies. These include modules in the module cache, vendored modules, and the standard library.

Since rules are applied both from client to server and server to client, rules with an empty string will be applied to all paths that it sees, so even dependencies will be mapped to "/path/to/module" .

We plan to make this easier in the future. Progress can be tracked in the issue tracker golang/vscode-go#1985 .

Debug sessions started with the "debug test" CodeLens or the test UI does not use my launch.json configuration

The "debug test" CodeLens and the test UI do not use the launch.json configuration ( Issue 855 ). As a workaround, use the go.delveConfig setting and the go.testFlags setting. Please note that these all apply to all debug sessions unless overwritten by a specific launch.json configuration.

Starting a debug session fails with

decoding dwarf section info at offset 0x0: too short or could not open debug info error

These errors indicate that your binary was built with linker flags that stripped the symbol table ( -s ) or the DWARF debug information ( -w ), making debugging impossible. If the binary is built while launching the session, make sure your launch.json configuration does not contain "buildFlags": "--ldflags '-s -w'" . If you use debug test or Test Explorer, check go.buildFlags in settings.json . If the binary is built externally, check the command-line flags and do not use go run . Unlike go build , go run passes -s -w to the linker under the hood. If you try to attach to such a binary with a debugger, it will fail with one of the above errors (see Go Issue 24833 ). Instead let dlv build the binary for you or use go build -gcflags=all="-N -l" .

Report issues

When you are having issues in dlv-dap mode, first check if the problems are reproducible after updating dlv and using the most recent version of dlv . It's possible that the problems are already fixed. You can also try to install dlv at tree head. Follow the instruction for updating dlv and updating extension .

Please report issues in our issue tracker with the following information.

• go version -m <path/to/dlv>
• VS Code and VS Code Go version (e.g. code --version )
• Instructions to reproduce the issue (code snippets, your launch.json , screenshot)
• DAP trace (See the instruction )

Collect logs

The logOutput and showLog attributes in launch.json enable Delve-side logging (server-side) and DAP message tracing. The trace attribute controls the verbosity of Go extension's side logging (client-side).

The logging will appear in the Go Debug output channel (Command Palette -> "View: Toggle Output" -> Select "Go Debug" from the dropdown menu). By nature, debug logs may contain sensitive information. Please review the logs carefully before sharing debug logs.

Development

Code location.

The core part of Delve DAP implementation is in the service/dap package. Follow Delve project's contribution guideline to send PRs.

Code for integration with the Go extension is mostly in src/goDebugFactory.ts and tests are in test/integration/goDebug.test.ts . Please take a look at VS Code Go project's contribution guideline to learn about how to prepare a change and send it for review.

For simple launch cases, build the dlv binary, and configure "go.alternateTools" setting.

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