Quickstart: Add feature flags to a Go Gin web app

2025-07-18

In this quickstart, you'll create a feature flag in Azure App Configuration and use it to dynamically control the availability of a new web page in a Go Gin web app without restarting or redeploying it.

The feature management support extends the dynamic configuration feature in App Configuration. This example demonstrates how to integrate feature flags into a Go Gin web application with real-time updates and conditional page rendering.

Prerequisites

An Azure account with an active subscription. Create one for free.
An App Configuration store. Create a store.
Go 1.21 or later. For information on installing Go, see the Go downloads page.
Azure App Configuration Go provider v1.1.0-beta.1 or later.

Create a feature flag

Add a feature flag called Beta to the App Configuration store and leave Label and Description with their default values. For more information about how to add feature flags to a store using the Azure portal or the CLI, go to Create a feature flag.

Create a Go web application

Create a new directory for your Go project and navigate into it:

mkdir gin-feature-flag-quickstart
cd gin-feature-flag-quickstart

Initialize a new Go module:

go mod init gin-feature-flag-quickstart

Install the required Go packages for Azure App Configuration, Gin web framework, and feature management:

go get github.com/gin-gonic/gin
go get github.com/microsoft/Featuremanagement-Go/featuremanagement
go get github.com/microsoft/Featuremanagement-Go/featuremanagement/providers/azappconfig

Create a templates directory for your HTML templates.
```
mkdir templates
```

Create an HTML template for the home page. Add the following content to templates/index.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{{.title}}</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
    <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
        <div class="container">
            <a class="navbar-brand" href="/">TestAppConfig</a>
            <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target=".navbar-collapse" aria-controls="navbarSupportedContent"
                    aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="navbar-collapse collapse d-sm-inline-flex justify-content-between">
                <ul class="navbar-nav flex-grow-1">
                    <li class="nav-item">
                        <a class="nav-link text-dark" href="/">Home</a>
                    </li>
                    {{if .betaEnabled}}
                    <li class="nav-item">
                        <a class="nav-link text-dark" href="/beta">Beta</a>
                    </li>
                    {{end}}
                </ul>
            </div>
        </div>
    </nav>    <div class="container">
        <div class="row justify-content-center">
            <div class="col-md-8 text-center">
                <h1>Hello from Azure App Configuration</h1>
        </div>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js"></script>
</body>
</html>

Create an HTML template for the beta page. Add the following content to templates/beta.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{{.title}}</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
    <!-- Navigation -->    <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
        <div class="container">
            <a class="navbar-brand" href="/">TestAppConfig</a>
            <div class="navbar-collapse collapse d-sm-inline-flex justify-content-between">
                <ul class="navbar-nav flex-grow-1">
                    <li class="nav-item">
                        <a class="nav-link text-dark" href="/">Home</a>
                    </li>
                    <li class="nav-item">
                        <a class="nav-link text-dark" href="/beta">Beta</a>
                    </li>
                </ul>
            </div>
        </div>
    </nav>    <div class="container">
        <div class="row justify-content-center">
            <div class="col-md-8 text-center">
                <h1>This is the beta website.</h1>
            </div>
        </div>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js"></script>
</body>
</html>

Use a feature flag

Update the options to enable feature flags in previous step.

    options := &azureappconfiguration.Options{
        FeatureFlagOptions: azureappconfiguration.FeatureFlagOptions{
            Enabled: true,
            RefreshOptions: azureappconfiguration.RefreshOptions{
                Enabled: true,
            },
        },
    }

Tip

When no selector is specified in FeatureFlagOptions, it loads all feature flags with no label in your App Configuration store. The default refresh interval of feature flags is 30 seconds. You can customize this behavior via the RefreshOptions parameter. For example, the following code snippet loads only feature flags that start with TestApp: in their key name and have the label dev. The code also changes the refresh interval time to 5 minutes. Note that this refresh interval time is separate from that for regular key-values.

FeatureFlagOptions{
    Enabled: true,
    Selectors: []azureappconfiguration.Selector{
        {
            KeyFilter:   "TestApp:*",
            LabelFilter: "dev",
        },
    },
    RefreshOptions: azureappconfiguration.RefreshOptions{
        Enabled: true,
        Interval: 5 * time.Minute,
    },
}

Create a file named main.go with the following content:

package main

import (
    "context"
    "fmt"
    "log"
    "net/http"
    "os"

    "github.com/Azure/AppConfiguration-GoProvider/azureappconfiguration"
    "github.com/gin-gonic/gin"
    "github.com/microsoft/Featuremanagement-Go/featuremanagement"
    "github.com/microsoft/Featuremanagement-Go/featuremanagement/providers/azappconfig"
)

type WebApp struct {
    featureManager *featuremanagement.FeatureManager
    appConfig      *azureappconfiguration.AzureAppConfiguration
}

func (app *WebApp) refreshMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        go func() {
            ctx := context.Background()
            if err := app.appConfig.Refresh(ctx); err != nil {
                log.Printf("Error refreshing configuration: %v", err)
            }
        }()
        c.Next()
    }
}

func (app *WebApp) featureMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        // Check if Beta feature is enabled
        betaEnabled, err := app.featureManager.IsEnabled("Beta")
        if err != nil {
            log.Printf("Error checking Beta feature: %v", err)
            betaEnabled = false
        }

        // Store feature flag status for use in templates
        c.Set("betaEnabled", betaEnabled)
        c.Next()
    }
}

func (app *WebApp) setupRoutes(r *gin.Engine) {
    r.Use(app.refreshMiddleware())
    r.Use(app.featureMiddleware())

    // Load HTML templates
    r.LoadHTMLGlob("templates/*.html")

    // Routes
    r.GET("/", app.homeHandler)
    r.GET("/beta", app.betaHandler)
}

// Home page handler
func (app *WebApp) homeHandler(c *gin.Context) {
    betaEnabled := c.GetBool("betaEnabled")

    c.HTML(http.StatusOK, "index.html", gin.H{
        "title":       "Feature Management Example App",
        "betaEnabled": betaEnabled,
    })
}

// Beta page handler
func (app *WebApp) betaHandler(c *gin.Context) {
    betaEnabled := c.GetBool("betaEnabled")

    if !betaEnabled {
        return
    }

    c.HTML(http.StatusOK, "beta.html", gin.H{
        "title": "Beta Page",
    })
}

func main() {
    ctx := context.Background()

    // Load Azure App Configuration
    appConfig, err := loadAzureAppConfiguration(ctx)
    if err != nil {
        log.Fatalf("Error loading Azure App Configuration: %v", err)
    }

    // Create feature flag provider
    featureFlagProvider, err := azappconfig.NewFeatureFlagProvider(appConfig)
    if err != nil {
        log.Fatalf("Error creating feature flag provider: %v", err)
    }

    // Create feature manager
    featureManager, err := featuremanagement.NewFeatureManager(featureFlagProvider, nil)
    if err != nil {
        log.Fatalf("Error creating feature manager: %v", err)
    }

    // Create web app
    app := &WebApp{
        featureManager: featureManager,
        appConfig:      appConfig,
    }

    // Set up Gin with default middleware (Logger and Recovery)
    r := gin.Default()

    // Set up routes
    app.setupRoutes(r)

    // Start server
    fmt.Println("Starting server on http://localhost:8080")
    fmt.Println("Open http://localhost:8080 in your browser")
    fmt.Println("Toggle the 'Beta' feature flag in Azure portal to see changes")
    fmt.Println()

    if err := r.Run(":8080"); err != nil {
        log.Fatalf("Failed to start server: %v", err)
    }
}

Run the web application

Set the environment variable for authentication and run the application.
```
go mod tidy
go run .
```
Open a browser window, and go to http://localhost:8080. Your browser should display a page similar to the image below.
Sign in to the Azure portal. Select All resources, and select the App Configuration store that you created previously.
Select Feature manager and locate the Beta feature flag. Enable the flag by selecting the checkbox under Enabled.
Refresh the browser a few times. When the refresh interval time window passes, the page displays with updated content:
Notice that the Beta menu item now appears in the navigation bar. Click on it to access the beta page:

Clean up resources

If you don't want to continue using the resources created in this article, delete the resource group you created here to avoid charges.

Important

Deleting a resource group is irreversible. The resource group and all the resources in it are permanently deleted. Ensure that you don't accidentally delete the wrong resource group or resources. If you created the resources for this article inside a resource group that contains other resources you want to keep, delete each resource individually from its respective pane instead of deleting the resource group.

Sign in to the Azure portal, and select Resource groups.
In the Filter by name box, enter the name of your resource group.
In the result list, select the resource group name to see an overview.
Select Delete resource group.
You're asked to confirm the deletion of the resource group. Enter the name of your resource group to confirm, and select Delete.

After a few moments, the resource group and all its resources are deleted.

Next steps

In this quickstart, you created a feature flag in Azure App Configuration and used it in a Go Gin web application. The Feature Management Go library provides feature flag capabilities that integrate seamlessly with Azure App Configuration.For more features, continue to the following document.

Go Feature Management reference

While a feature flag allows you to activate or deactivate functionality in your app, you may want to customize a feature flag based on your app's logic. Feature filters allow you to enable a feature flag conditionally. For more information, continue to the following tutorial.

Enable conditional features with feature filters

Azure App Configuration offers built-in feature filters that enable you to activate a feature flag only during a specific period or to a particular targeted audience of your app. For more information, continue to the following tutorial.

Enable features on a schedule

Roll out features to targeted audiences