Graceful shutdown trong Go server thế nào?

srv := &http.Server{Addr: ":8080", Handler: mux}
go func() {
    if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
        log.Fatal(err)
    }
}()

// Bắt SIGINT / SIGTERM (Ctrl+C, kubectl rollout, docker stop)
quit := make(chan os.Signal, 1)
signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
<-quit

// Cho phép request đang chạy 30s để hoàn thành
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
if err := srv.Shutdown(ctx); err != nil {
    log.Fatalf("forced shutdown: %v", err)
}