gracefully shutdown HTTP server

	// listen to OS signals and gracefully shutdown HTTP server
	stopped := make(chan struct{})
	go func() {
		sigint := make(chan os.Signal, 1)
		signal.Notify(sigint, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
		<-sigint
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		if err := srv.Shutdown(ctx); err != nil {
			log.Printf("HTTP Server Shutdown Error: %v", err)
		}
		close(stopped)
	}()

	log.Printf("Starting HTTP server on %s", cfg.HTTPAddr)

	// start HTTP server
	if err := srv.ListenAndServe(); err != http.ErrServerClosed {
		log.Fatalf("HTTP server ListenAndServe Error: %v", err)
	}

	<-stopped