httptest-server.go

func newLocalListener() net.Listener {
	if serveFlag != "" {
		l, err := net.Listen("tcp", serveFlag)
		if err != nil {
			panic(fmt.Sprintf("httptest: failed to listen on %v: %v", serveFlag, err))
		}
		return l
	}
	l, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		if l, err = net.Listen("tcp6", "[::1]:0"); err != nil {
			panic(fmt.Sprintf("httptest: failed to listen on a port: %v", err))
		}
	}
	return l
}

func NewUnstartedServer(handler http.Handler) *Server {
	return &Server{
		Listener: newLocalListener(),
		Config:   &http.Server{Handler: handler},
	}
}

func (s *Server) Start() {
	if s.URL != "" {
		panic("Server already started")
	}
	if s.client == nil {
		s.client = &http.Client{Transport: &http.Transport{}}
	}
	s.URL = "http://" + s.Listener.Addr().String()
	s.wrap()
	s.goServe()
	if serveFlag != "" {
		fmt.Fprintln(os.Stderr, "httptest: serving on", s.URL)
		select {}
	}
}

func (s *Server) goServe() {
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		s.Config.Serve(s.Listener)
	}()
}