golang-uber-fx

Inject fx.Lifecycle into your server constructor and append an fx.Hook. Call net.Listen and launch srv.Serve in a goroutine inside OnStart so the hook returns quickly, and call srv.Shutdown(ctx) in OnStop for graceful shutdown.

fx is built on dig and shares the same DI primitives, but adds lifecycle hooks, a module system with scoped decorators, a signal-aware run loop, and structured event logging. Use fx for long-running services and raw dig for CLI tools or libraries that manage their own lifecycle.

Wrap the constructor with fx.Annotate and pass fx.As(new(YourInterface)), optionally adding fx.ResultTags for name or group tags. This keeps the original constructor unchanged and avoids writing a separate adapter or fx.Out struct.

Use fxtest.New(t, ...) with fx.Replace to swap a real provider for a fake, and fx.Populate(&target) to pull a service out of the graph. Call app.RequireStart() and defer app.RequireStop() so failures fail the test and cleanup runs automatically.

Startup hangs when an OnStart hook runs blocking work synchronously instead of spawning a goroutine, preventing dependent hooks from firing. Hooks must return quickly and respect context cancellation within the configured StartTimeout, which defaults to 15 seconds.

Use fx.Supply for pre-built values such as parsed config, secrets, or command-line flags that already exist before fx.New runs. It avoids writing a no-op constructor like fx.Provide(func() *Config { return cfg }) and makes intent clearer.