教學課程：在 Go Gin Web 應用程式中使用變化功能旗標

在本教學課程中，您使用變體功能旗標來管理範例應用程式 Quote of the Day 中不同使用者區隔的體驗。您利用使用變體功能旗標 (部分機器翻譯) 中所建立的變體功能旗標。繼續之前，請確定您在應用程式組態存放區中建立名為 Greeting 的變體功能旗標。

先決條件

具有有效訂閱的 Azure 帳戶。免費創建一個。
應用程式組態存放區，如建立存放區指引所示。
轉到 1.21 或更高版本。如需安裝 Go 的相關資訊，請參閱 Go 下載頁面。
Azure App Configuration Go 提供者 v1.1.0 或更新版本。
功能管理 Go 程式庫 v1.1.0 或更新版本。
請遵循使用變體功能旗標 (部分機器翻譯) 教學課程，然後建立名為 Greeting 的變體功能旗標。

設定 Go Gin Web 應用程式

為您的 Go 專案建立一個新目錄並導航到其中：
```
mkdir quote-of-the-day
cd quote-of-the-day
```
初始化一個新的Go模組：
```
go mod init quote-of-the-day
```

安裝必要的 Go 套件：

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

為您的HTML範本建立範本目錄，並新增所需的HTML檔案：
```
mkdir templates
```
從 GitHub 存放庫新增下列 HTML 範本檔案，並將其放在目錄中 templates ：
- index.html - 首頁範本
- login.html - 登入頁面範本

建立具有下列內容的檔案 appconfig.go 。您可以使用 Microsoft Entra ID (建議) 或連接字串連線到應用程式組態存放區。

Microsoft Entra ID (建議)
連接字串

package main

import (
    "context"
    "log"
    "os"

    "github.com/Azure/AppConfiguration-GoProvider/azureappconfiguration"
    "github.com/Azure/azure-sdk-for-go/sdk/azidentity"
)

func loadAzureAppConfiguration(ctx context.Context) (*azureappconfiguration.AzureAppConfiguration, error) {
    // Get the endpoint from environment variable
    endpoint := os.Getenv("AZURE_APPCONFIG_ENDPOINT")
    if endpoint == "" {
        log.Fatal("AZURE_APPCONFIG_ENDPOINT environment variable is not set")
    }

    // Create a credential using DefaultAzureCredential
    credential, err := azidentity.NewDefaultAzureCredential(nil)
    if err != nil {
        log.Fatalf("Failed to create credential: %v", err)
    }

    // Set up authentication options with endpoint and credential
    authOptions := azureappconfiguration.AuthenticationOptions{
        Endpoint:   endpoint,
        Credential: credential,
    }

    // Set up options to enable feature flags
    options := &azureappconfiguration.Options{
        FeatureFlagOptions: azureappconfiguration.FeatureFlagOptions{
            Enabled: true,
            RefreshOptions: azureappconfiguration.RefreshOptions{
                Enabled: true,
            },
        },
    }

    // Load configuration from Azure App Configuration
    appConfig, err := azureappconfiguration.Load(ctx, authOptions, options)
    if err != nil {
        log.Fatalf("Failed to load configuration: %v", err)
    }

    return appConfig, nil
}

package main

import (
    "context"
    "log"
    "os"

    "github.com/Azure/AppConfiguration-GoProvider/azureappconfiguration"
)

func loadAzureAppConfiguration(ctx context.Context) (*azureappconfiguration.AzureAppConfiguration, error) {
    // Get the connection string from environment variable
    connectionString := os.Getenv("AZURE_APPCONFIG_CONNECTION_STRING")
    if connectionString == "" {
        log.Fatal("AZURE_APPCONFIG_CONNECTION_STRING environment variable is not set")
    }

    // Set up authentication options with connection string
    authOptions := azureappconfiguration.AuthenticationOptions{
        ConnectionString: connectionString,
    }

    // Set up options to enable feature flags
    options := &azureappconfiguration.Options{
        FeatureFlagOptions: azureappconfiguration.FeatureFlagOptions{
            Enabled: true,
            RefreshOptions: azureappconfiguration.RefreshOptions{
                Enabled: true,
            },
        },
    }

    // Load configuration from Azure App Configuration
    appConfig, err := azureappconfiguration.Load(ctx, authOptions, options)
    if err != nil {
        log.Fatalf("Failed to load configuration: %v", err)
    }

    return appConfig, nil
}

使用變化功能旗標

使用下列內容建立名為 main.go 的檔案：

package main

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

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

type Quote struct {
    Message string `json:"message"`
    Author  string `json:"author"`
}

type WebApp struct {
    featureManager *featuremanagement.FeatureManager
    appConfig      *azureappconfiguration.AzureAppConfiguration
    quotes         []Quote
}

func main() {
    // Load Azure App Configuration
    appConfig, err := loadAzureAppConfiguration(context.Background())
    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)
    }

    // Initialize quotes
    quotes := []Quote{
        {
            Message: "You cannot change what you are, only what you do.",
            Author:  "Philip Pullman",
        },
    }

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

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

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

    fmt.Println("Starting Quote of the Day server on http://localhost:8080")
    fmt.Println("Open http://localhost:8080 in your browser")
    fmt.Println()
}

使用中介軟體，從 Azure 應用程式組態啟用設定和功能旗標重新整理。

// Existing code
// ... ...

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

使用下列內容設定路由：

// Existing code
// ... ...

func (app *WebApp) setupRoutes(r *gin.Engine) {
    // Setup sessions
    store := cookie.NewStore([]byte("secret-key-change-in-production"))
    store.Options(sessions.Options{
        MaxAge:   3600, // 1 hour
        HttpOnly: true,
        Secure:   false, // Set to true in production with HTTPS
    })
    r.Use(sessions.Sessions("session", store))

    r.Use(app.refreshMiddleware())

    // Load HTML templates
    r.LoadHTMLGlob("templates/*.html")
    // Routes
    r.GET("/", app.homeHandler)
    r.GET("/login", app.loginPageHandler)
    r.POST("/login", app.loginHandler)
    r.GET("/logout", app.logoutHandler)
}

// Home page handler
func (app *WebApp) homeHandler(c *gin.Context) {
    session := sessions.Default(c)
    username := session.Get("username")
    quote := app.quotes[0]

    var greetingMessage string
    var targetingContext featuremanagement.TargetingContext
    if username != nil {
        // Create targeting context for the user
        targetingContext = createTargetingContext(username.(string))

        // Get the Greeting variant for the current user
        if variant, err := app.featureManager.GetVariant("Greeting", targetingContext); err != nil {
            log.Printf("Error getting Greeting variant: %v", err)
        } else if variant != nil && variant.ConfigurationValue != nil {
            // Extract the greeting message from the variant configuration
            if configValue, ok := variant.ConfigurationValue.(string); ok {
                greetingMessage = configValue
            }
        }
    }

    c.HTML(http.StatusOK, "index.html", gin.H{
        "title":           "Quote of the Day",
        "user":            username,
        "greetingMessage": greetingMessage,
        "quote":           quote,
    })
}

func (app *WebApp) loginPageHandler(c *gin.Context) {
    c.HTML(http.StatusOK, "login.html", gin.H{
        "title": "Login - Quote of the Day",
    })
}

func (app *WebApp) loginHandler(c *gin.Context) {
    email := strings.TrimSpace(c.PostForm("email"))

    // Basic validation
    if email == "" {
        c.HTML(http.StatusOK, "login.html", gin.H{
            "title": "Login - Quote of the Day",
            "error": "Email cannot be empty",
        })
        return
    }

    if !strings.Contains(email, "@") {
        c.HTML(http.StatusOK, "login.html", gin.H{
            "title": "Login - Quote of the Day",
            "error": "Please enter a valid email address",
        })
        return
    }

    // Store email in session
    session := sessions.Default(c)
    session.Set("username", email)
    if err := session.Save(); err != nil {
        log.Printf("Error saving session: %v", err)
    }

    c.Redirect(http.StatusFound, "/")
}

func (app *WebApp) logoutHandler(c *gin.Context) {
    session := sessions.Default(c)
    session.Clear()
    if err := session.Save(); err != nil {
        log.Printf("Error saving session: %v", err)
    }
    c.Redirect(http.StatusFound, "/")
}

// Helper function to create TargetingContext
func createTargetingContext(userID string) featuremanagement.TargetingContext {
    targetingContext := featuremanagement.TargetingContext{
        UserID: userID,
        Groups: []string{},
    }

    if strings.Contains(userID, "@") {
        parts := strings.Split(userID, "@")
        if len(parts) == 2 {
            domain := parts[1]
            targetingContext.Groups = append(targetingContext.Groups, domain) // Add domain as group
        }
    }

    return targetingContext
}
// The rest of existing code
//... ...

使用下列內容更新 main.go：

// Existing code
// ... ...
 r := gin.Default()

 // Setup routes
 app.setupRoutes(r)

 // Start server
 if err := r.Run(":8080"); err != nil {
    log.Fatalf("Failed to start server: %v", err)
}
// The rest of existing code
// ... ...

建置並執行應用程式

設定用於驗證的環境變數，並執行應用程式：
```
go mod tidy
go run .
```
開啟瀏覽器並巡覽至 http://localhost:8080。選取右上方的 [登入] 以 usera@contoso.com 身分登入。
登入後，您會看到給 usera@contoso.com 的一則長問候訊息。
按一下 [登出] 並以 userb@contoso.com 身分登入，您會看到簡單問候訊息。

備註

請務必讓本教學課程正確使用這些名稱。只要功能如預期般設定，這兩個使用者應該會看到不同的變體。