Merge pull request #303307 from linglingye001/go/fm/custom

Go Gin web app in custom filter scenario

Author: v-ccolin

articles/azure-app-configuration/TOC.yml

@@ -200,6 +200,8 @@
       href: howto-feature-filters-javascript.md
     - name: Python
       href: howto-feature-filters-python.md
+    - name: Go Gin
+      href: howto-feature-filters-go.md
   - name: Enable features on a schedule
     items:
     - name: Overview

articles/azure-app-configuration/concept-feature-management.md

@@ -96,6 +96,12 @@ To start using feature flags with Azure App Configuration, continue to the follo
 > [!div class="nextstepaction"]
 > [JavaScript](./quickstart-feature-flag-javascript.md)
 
+> [!div class="nextstepaction"]
+> [Go](./quickstart-feature-flag-go-console.md)
+
+> [!div class="nextstepaction"]
+> [Go Gin](./quickstart-feature-flag-go-gin.md)
+
 > [!div class="nextstepaction"]
 > [Azure Kubernetes Service](./quickstart-feature-flag-azure-kubernetes-service.md)
 

articles/azure-app-configuration/howto-feature-filters-go.md

@@ -0,0 +1,124 @@
+---
+title: Enable conditional features with a custom filter in a Go Gin web application
+titleSuffix: Azure App Configuration
+description: Learn how to implement a custom feature filter to enable conditional feature flags for your Go Gin web application.
+ms.service: azure-app-configuration
+ms.devlang: golang
+author: linglingye
+ms.author: linglingye
+ms.topic: how-to
+ms.custom: devx-track-go, mode-other
+ms.date: 07/25/2025
+---
+
+# Enable conditional features with a custom filter in a Go Gin web application
+
+Feature flags can use feature filters to enable features conditionally. To learn more about feature filters, see [Enable conditional features with feature filters](./howto-feature-filters.md).
+
+The example used in this guide is based on the Go Gin web application introduced in the feature management [quickstart](./quickstart-feature-flag-go-gin.md). Before proceeding further, complete the quickstart to create a Go Gin web application with a *Beta* feature flag. Once completed, you must [add a custom feature filter](./howto-feature-filters.md) to the *Beta* feature flag in your App Configuration store. 
+
+In this guide, you learn how to implement a custom feature filter and use the feature filter to enable features conditionally.
+
+## Prerequisites
+
+- Create a [Go Gin web application with a feature flag](./quickstart-feature-flag-go-gin.md).
+- [Add a custom feature filter to the feature flag](./howto-feature-filters.md)
+
+## Implement a custom feature filter
+
+You added a custom feature filter named **Random** with a **Percentage** parameter for your *Beta* feature flag in the prerequisites. Next, you'll implement the feature filter to enable the *Beta* feature flag based on the chance defined by the **Percentage** parameter.
+
+1. Create a `random_filter.go` file with the following code:
+
+    ```golang
+    package main
+
+    import (
+        "fmt"
+        "math/rand"
+        "time"
+
+        "github.com/microsoft/Featuremanagement-Go/featuremanagement"
+    )
+
+    type RandomFilter struct{}
+
+    func (f *RandomFilter) Name() string {
+        return "Random"
+    }
+
+    func (f *RandomFilter) Evaluate(evalCtx featuremanagement.FeatureFilterEvaluationContext, appCtx any) (bool, error) {
+        percentage, ok := evalCtx.Parameters["Percentage"].(float64)
+        if !ok {
+            return false, fmt.Errorf("invalid parameter type for Percentage: expected float64, got %T", evalCtx.Parameters["Percentage"])
+        }
+
+        rand.Seed(time.Now().UnixNano())
+        randomValue := rand.Intn(100)
+        return randomValue <= int(percentage), nil
+    }
+    ```
+
+    You added a `RandomFilter` struct that implements the `FeatureFilter` interface from the `featuremanagement` library. The `FeatureFilter` interface has two methods:
+    - `Name()` returns the filter name **Random**, which matches the filter name you set in the *Beta* feature flag in Azure App Configuration.
+    - `Evaluate()` is called whenever a feature flag is evaluated. A feature filter enables a feature flag by returning `true`.
+
+2. Update your `main.go` file to register the `RandomFilter` when creating the feature manager:
+
+    ```golang
+    // ...existing code...
+
+    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)
+        }
+
+        // Register custom filters
+        options := &featuremanagement.Options{
+            Filters: []featuremanagement.FeatureFilter{
+                &RandomFilter{},
+            },
+        }
+
+        // Create feature manager with custom filters
+        featureManager, err := featuremanagement.NewFeatureManager(featureFlagProvider, options)
+        if err != nil {
+            log.Fatalf("Error creating feature manager: %v", err)
+        }
+
+        // ...existing code...
+    }
+    ```
+
+## Feature filter in action
+
+Relaunch the application and refresh the browser a few times. Without manually toggling the feature flag, the **Beta** menu appears randomly based on the percentage you set.
+
+:::image type="content" source="./media/quickstarts/gin-app-feature-flag-before.png" alt-text="Screenshot of Gin web app with Beta menu hidden.":::
+
+:::image type="content" source="./media/quickstarts/gin-app-feature-flag-after.png" alt-text="Screenshot of Gin web app with Beta menu.":::
+
+## Next steps
+
+To learn more about the built-in feature filters, continue to the following documents.
+
+> [!div class="nextstepaction"]
+> [Enable features on a schedule](./howto-timewindow-filter.md)
+
+> [!div class="nextstepaction"]
+> [Roll out features to targeted audience](./howto-targetingfilter.md)
+
+For the full feature rundown of the Go feature management library, continue to the following document.
+
+> [!div class="nextstepaction"]
+> [Go Feature Management reference](https://pkg.go.dev/github.com/microsoft/Featuremanagement-Go/featuremanagement)

articles/azure-app-configuration/howto-feature-filters.md

@@ -62,6 +62,7 @@ You can create custom feature filters that enable features based on your specifi
     - [ASP.NET Core](./howto-feature-filters-aspnet-core.md)
     - [Node.js](./howto-feature-filters-javascript.md)
     - [Python](./howto-feature-filters-python.md)
+    - [Go Gin](./howto-feature-filters-go.md)
 
 ## Next steps