Quickstart: Create a Go or Rust function in Azure using Visual Studio Code

In this article, you use Visual Studio Code to create a custom handler function that responds to HTTP requests. After testing the code locally, you deploy it to the serverless environment of Azure Functions.

Custom handlers can be used to create functions in any language or runtime by running an HTTP server process. This article supports both Go and Rust.

Completing this quickstart incurs a small cost of a few USD cents or less in your Azure account.

Configure your environment

Before you get started, make sure you have the following requirements in place:

Create your local project

In this section, you use Visual Studio Code to create a local Azure Functions custom handlers project. Later in this article, you'll publish your function code to Azure.

  1. Choose the Azure icon in the Activity bar, then in the Azure: Functions area, select the Create new project... icon.

    Choose Create a new project

  2. Choose a directory location for your project workspace and choose Select.


    These steps were designed to be completed outside of a workspace. In this case, do not select a project folder that is part of a workspace.

  3. Provide the following information at the prompts:

    • Select a language for your function project: Choose Custom.

    • Select a template for your project's first function: Choose HTTP trigger.

    • Provide a function name: Type HttpExample.

    • Authorization level: Choose Anonymous, which enables anyone to call your function endpoint. To learn about authorization level, see Authorization keys.

    • Select how you would like to open your project: Choose Add to workspace.

  4. Using this information, Visual Studio Code generates an Azure Functions project with an HTTP trigger function. You can view the local project files in the Explorer. To learn more about files that are created, see Generated project files.

Create and build your function

The function.json file in the HttpExample folder declares an HTTP trigger function. You complete the function by adding a handler and compiling it into an executable.

  1. Press Ctrl + N (Cmd + N on macOS) to create a new file. Save it as handler.go in the function app root (in the same folder as host.json).

  2. In handler.go, add the following code and save the file. This is your Go custom handler.

    package main
    import (
    func helloHandler(w http.ResponseWriter, r *http.Request) {
        message := "This HTTP triggered function executed successfully. Pass a name in the query string for a personalized response.\n"
        name := r.URL.Query().Get("name")
        if name != "" {
            message = fmt.Sprintf("Hello, %s. This HTTP triggered function executed successfully.\n", name)
        fmt.Fprint(w, message)
    func main() {
        listenAddr := ":8080"
        if val, ok := os.LookupEnv("FUNCTIONS_CUSTOMHANDLER_PORT"); ok {
            listenAddr = ":" + val
        http.HandleFunc("/api/HttpExample", helloHandler)
        log.Printf("About to listen on %s. Go to", listenAddr, listenAddr)
        log.Fatal(http.ListenAndServe(listenAddr, nil))
  3. Press Ctrl + Shift + ` or select New Terminal from the Terminal menu to open a new integrated terminal in VS Code.

  4. Compile your custom handler using the following command. An executable file named handler (handler.exe on Windows) is output in the function app root folder.

    go build handler.go

    VS Code - Build Go custom handler

Configure your function app

The function host needs to be configured to run your custom handler binary when it starts.

  1. Open host.json.

  2. In the customHandler.description section, set the value of defaultExecutablePath to handler (on Windows, set it to handler.exe).

  3. In the customHandler section, add a property named enableForwardingHttpRequest and set its value to true. For functions consisting of only an HTTP trigger, this setting simplifies programming by allow you to work with a typical HTTP request instead of the custom handler request payload.

  4. Confirm the customHandler section looks like this example. Save the file.

    "customHandler": {
      "description": {
        "defaultExecutablePath": "handler",
        "workingDirectory": "",
        "arguments": []
      "enableForwardingHttpRequest": true

The function app is configured to start your custom handler executable.

Run the function locally

You can run this project on your local development computer before you publish to Azure.

  1. In the integrated terminal, start the function app using Azure Functions Core Tools.

    func start
  2. With Core Tools running, navigate to the following URL to execute a GET request, which includes ?name=Functions query string.


  3. A response is returned, which looks like the following in a browser:

    Browser - localhost example output

  4. Information about the request is shown in Terminal panel.

    Task host start - VS Code terminal output

  5. Press Ctrl + C to stop Core Tools.

After you've verified that the function runs correctly on your local computer, it's time to use Visual Studio Code to publish the project directly to Azure.

Sign in to Azure

Before you can publish your app, you must sign in to Azure.

  1. If you aren't already signed in, choose the Azure icon in the Activity bar, then in the Azure: Functions area, choose Sign in to Azure.... If you don't already have one, you can Create a free Azure account. Students can create a free Azure account for Students.

    Sign in to Azure within VS Code

    If you're already signed in, go to the next section.

  2. When prompted in the browser, choose your Azure account and sign in using your Azure account credentials.

  3. After you've successfully signed in, you can close the new browser window. The subscriptions that belong to your Azure account are displayed in the Side bar.

Compile the custom handler for Azure

In this section, you publish your project to Azure in a function app running Linux. In most cases, you must recompile your binary and adjust your configuration to match the target platform before publishing it to Azure.

  1. In the integrated terminal, compile the handler to Linux/x64. A binary named handler is created in the function app root.

    GOOS=linux GOARCH=amd64 go build handler.go

Publish the project to Azure

In this section, you create a function app and related resources in your Azure subscription and then deploy your code.


Publishing to an existing function app overwrites the content of that app in Azure.

  1. Choose the Azure icon in the Activity bar, then in the Azure: Functions area, choose the Deploy to function app... button.

    Publish your project to Azure

  2. Provide the following information at the prompts:

    • Select folder: Choose a folder from your workspace or browse to one that contains your function app. You won't see this if you already have a valid function app opened.

    • Select subscription: Choose the subscription to use. You won't see this if you only have one subscription.

    • Select Function App in Azure: Choose + Create new Function App (advanced).


      The advanced option lets you choose the specific operating system on which your function app runs in Azure, which in this case is Linux.

      VS Code - Select advanced create new function app

    • Enter a globally unique name for the function app: Type a name that is valid in a URL path. The name you type is validated to make sure that it's unique in Azure Functions.

    • Select a runtime stack: Choose Custom Handler.

    • Select an OS: Choose Linux.

    • Select a hosting plan: Choose Consumption.

    • Select a resource group: Choose + Create new resource group. Enter a name for the resource group. This name must be unique within your Azure subscription. You can use the name suggested in the prompt.

    • Select a storage account: Choose + Create new storage account. This name must be globally unique within Azure. You can use the name suggested in the prompt.

    • Select an Application Insights resource: Choose + Create Application Insights resource. This name must be globally unique within Azure. You can use the name suggested in the prompt.

    • Select a location for new resources: For better performance, choose a region near you.The extension shows the status of individual resources as they are being created in Azure in the notification area.

    Notification of Azure resource creation

  3. When completed, the following Azure resources are created in your subscription:

    • A resource group, which is a logical container for related resources.
    • A standard Azure Storage account, which maintains state and other information about your projects.
    • A consumption plan, which defines the underlying host for your serverless function app.
    • A function app, which provides the environment for executing your function code. A function app lets you group functions as a logical unit for easier management, deployment, and sharing of resources within the same hosting plan.
    • An Application Insights instance connected to the function app, which tracks usage of your serverless function.

    A notification is displayed after your function app is created and the deployment package is applied.

  4. Select View Output in this notification to view the creation and deployment results, including the Azure resources that you created. If you miss the notification, select the bell icon in the lower right corner to see it again.

    Create complete notification

Run the function in Azure

  1. Back in the Azure: Functions area in the side bar, expand your subscription, your new function app, and Functions. Right-click (Windows) or Ctrl - click (macOS) the HttpExample function and choose Execute Function Now....

    Execute function now in Azure from Visual Studio Code

  2. In Enter request body you see the request message body value of { "name": "Azure" }. Press Enter to send this request message to your function.

  3. When the function executes in Azure and returns a response, a notification is raised in Visual Studio Code.

Clean up resources

When you continue to the next step and add an Azure Storage queue binding to your function, you'll need to keep all your resources in place to build on what you've already done.

Otherwise, you can use the following steps to delete the function app and its related resources to avoid incurring any further costs.

  1. In Visual Studio Code, press F1 to open the command palette. In the command palette, search for and select Azure Functions: Open in portal.

  2. Choose your function app, and press Enter. The function app page opens in the Azure portal.

  3. In the Overview tab, select the named link next to Resource group.

    Select the resource group to delete from the function app page.

  4. In the Resource group page, review the list of included resources, and verify that they are the ones you want to delete.

  5. Select Delete resource group, and follow the instructions.

    Deletion may take a couple of minutes. When it's done, a notification appears for a few seconds. You can also select the bell icon at the top of the page to view the notification.

To learn more about Functions costs, see Estimating Consumption plan costs.

Next steps