از LaunchDarkly (LD) با Golang – Dev Community استفاده کنید

go get "github.com/launchdarkly/go-server-sdk/v7"

package main

import (
    "log"
    "os"
    "os/signal"
    "syscall"
    "time"
    "github.com/launchdarkly/go-sdk-common/v3/ldcontext"
    "github.com/launchdarkly/go-sdk-common/v3/ldvalue"
    ld "github.com/launchdarkly/go-server-sdk/v7"
)

// Replace with your actual LaunchDarkly SDK key
const sdkKey = "YOUR-SDK-KEY"

// Replace with the key of the JSON flag you want to evaluate
const jsonFlagKey = "json-flag"


func main() {
    // --- 1. Configure and Initialize the LaunchDarkly Client (v7) ---

    // Optional: for advanced configuration like logging
    // config := ld.Config{} // Default configuration
    // client, err := ld.MakeCustomClient(sdkKey, config, 5*time.Second)

    // Creating client with Default configuration
    client, err := ld.MakeClient(sdkKey, 5*time.Second)
    if err != nil {
        log.Fatalf("Error initializing LaunchDarkly client: %v", err)
    }
    defer func() {
        if err := client.Close(); err != nil {
            log.Printf("Error closing LaunchDarkly client: %v", err)
        }
    }()

    if !client.Initialized() {
        log.Println("Client did not initialize successfully within the timeout.")
    } else {
        log.Println("LaunchDarkly client initialized successfully.")
    }

    // --- 2. Define the Evaluation Context (v7 uses ldcontext from common v3) ---
    evaluationContext := ldcontext.New("example-context-key")
    // Add more attributes as needed:
    // evaluationContext = ldcontext.NewBuilder("example-user-key").
    //  Kind("user").
    //  Name("Example User").
    //  SetString("email", "user@example.com").
    //  Build()

    // --- 3. Read the Initial JSON Flag Value (v7 uses ldvalue from common v3) ---
    defaultValue := ldvalue.ObjectBuild().Build()
    jsonValue, err := client.JSONVariation(jsonFlagKey, evaluationContext, defaultValue)
    if err != nil {
        log.Printf("Error evaluating flag '%s': %v. Using default value.", jsonFlagKey, err)
    }
    log.Printf("Initial value for flag '%s': %s\n", jsonFlagKey, jsonValue.JSONString())

    // --- 4. Watch for Flag Changes (v7 Flag Tracker with Listener Function) ---
    WatchFlagChanges(client, jsonFlagKey, evaluationContext)

    // --- 5. Keep the Application Running ---
    log.Println("Application started. Watching for flag changes. Press Ctrl+C to exit.")

    // Wait for a termination signal (Ctrl+C)
    quit := make(chan os.Signal, 1)
    signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
    <-quit

}

func WatchFlagChanges(client *ld.LDClient, flagKey string, context ldcontext.Context) {
    updateCh := client.GetFlagTracker().AddFlagValueChangeListener(flagKey, context, ldvalue.Null())
    go func() {
        for event := range updateCh {
            log.Printf("Flag %q for context %q has changed from %s to %s", event.Key,
                context.Key(), event.OldValue, event.NewValue)
        }
    }()
}