golang-uber-fx

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

Use fxtest.New with fx.Replace to override a previously-provided type, even one buried inside a module, without rewriting the module. Combine with fx.Populate to extract the service under test and app.RequireStart/RequireStop for lifecycle management.

A blocking OnStart hook is the usual cause — long-running work must run in a goroutine so the hook returns quickly and dependent hooks can fire. Also verify every provided type is reachable from an fx.Invoke, since unreferenced constructors never run.

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

Avoid fx for one-shot CLI tools or small object graphs where lifecycle hooks and signal handling add no value. Use raw uber-go/dig for wiring without a framework, or manual constructor injection when the graph is very small.