func (srv *Server) Shutdown() error {
	srv.listenerMutex.Lock()
	if srv.listener == nil {
		srv.listenerMutex.Unlock()
		return http.ErrServerClosed
	}
	srv.listenerMutex.Unlock()

	if atomic.AddUint32(&srv.inShutdown, 1) > 1 {
		// shutdown in progress
		return http.ErrServerClosed
	}

	// Close underneath HTTP listener.
	srv.listenerMutex.Lock()
	err := srv.listener.Close()
	srv.listenerMutex.Unlock()

		// send signal to various go-routines that they need to quit.
		cancelGlobalContext()

		if httpServer := newHTTPServerFn(); httpServer != nil {
			if err := httpServer.Shutdown(); err != nil && !errors.Is(err, http.ErrServerClosed) {
				shutdownLogIf(context.Background(), err)
			}
		}

		if objAPI := newObjectLayerFn(); objAPI != nil {
			shutdownLogIf(context.Background(), objAPI.Shutdown(context.Background()))
		}

	r.HandleFunc(attrPath, handleAttrs(attrs)).Methods("GET")

	srv := &http.Server{Addr: addr, Handler: r}

	go func() {
		if err := srv.ListenAndServe(); err != http.ErrServerClosed {
			log.Fatalf("listen: %v\n", err)
		}
	}()
	return srv

// If srv.Addr is blank, ":http" is used.
//
// ListenAndServe always returns a non-nil error. After [Server.Shutdown] or [Server.Close],
// the returned error is [ErrServerClosed].
func (srv *Server) ListenAndServe() error {
	if srv.shuttingDown() {
		return ErrServerClosed
	}
	addr := srv.Addr
	if addr == "" {
		addr = ":http"
	}
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}

	switch {
	// A peer node can be in shut down phase and proactively
	// return 503 server closed error, consider it as an offline node
	case strings.Contains(err.Error(), http.ErrServerClosed.Error()):
		return true
	// Corner case, the server closed the connection with a keep-alive timeout
	// some requests are not retried internally, such as POST request with written body

func TestServerShutdownThenServe(t *testing.T) {
	var srv Server
	cl := &countCloseListener{Listener: nil}
	srv.Shutdown(context.Background())
	got := srv.Serve(cl)
	if got != ErrServerClosed {
		t.Errorf("Serve err = %v; want ErrServerClosed", got)
	}
	nclose := atomic.LoadInt32(&cl.closes)
	if nclose != 1 {
		t.Errorf("Close calls = %v; want 1", nclose)
	}
}

		{"ErrMissingFile", Var, 0},
		{"ErrNoCookie", Var, 0},
		{"ErrNoLocation", Var, 0},
		{"ErrNotMultipart", Var, 0},
		{"ErrNotSupported", Var, 0},
		{"ErrSchemeMismatch", Var, 21},
		{"ErrServerClosed", Var, 8},
		{"ErrShortBody", Var, 0},
		{"ErrSkipAltProtocol", Var, 6},
		{"ErrUnexpectedTrailer", Var, 0},
		{"ErrUseLastResponse", Var, 7},
		{"ErrWriteAfterFlush", Var, 0},
		{"Error", Func, 0},