How do you manage the full lifecycle of a Go microservice from startup to shutdown?

A production Go service follows a structured lifecycle: configuration validation, dependency initialisation, readiness signalling, traffic serving, graceful shutdown on signal, and cleanup. Each phase must handle failures correctly.

func main() {
    // Phase 1: load and validate config — fail fast
    cfg, err := config.Load()
    if err != nil { log.Fatalf("invalid config: %v", err) }

    // Phase 2: initialise dependencies
    logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
        Level: cfg.LogLevel,
    }))
    slog.SetDefault(logger)

    db, err := database.Open(cfg.Database)
    if err != nil { log.Fatalf("database: %v", err) }
    defer db.Close()

    // Phase 3: build services
    userRepo := postgres.NewUserRepository(db)
    userSvc  := service.NewUserService(userRepo)
    router   := api.NewRouter(userSvc)

    // Phase 4: start server
    srv := &http.Server{
        Addr:         fmt.Sprintf(":%d", cfg.Port),
        Handler:      router,
        ReadTimeout:  5 * time.Second,
        WriteTimeout: 10 * time.Second,
    }

    errCh := make(chan error, 1)
    go func() {
        slog.Info("server starting", "port", cfg.Port)
        if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
            errCh <- err
        }
    }()

    // Phase 5: wait for shutdown or error
    sigCh := make(chan os.Signal, 1)
    signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)

    select {
    case err := <-errCh:
        slog.Error("server error", "err", err)
    case sig := <-sigCh:
        slog.Info("shutdown signal", "signal", sig)
    }

    // Phase 6: graceful shutdown
    shutdownCtx, cancel := context.WithTimeout(context.Background(), 25*time.Second)
    defer cancel()
    if err := srv.Shutdown(shutdownCtx); err != nil {
        slog.Error("shutdown error", "err", err)
    }
    slog.Info("service stopped cleanly")
}

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