return
	}
	// for testing.
	if s.statusPort == 0 {
		_, hostPort, _ := net.SplitHostPort(l.Addr().String())
		allocatedPort, _ := strconv.Atoi(hostPort)
		s.mutex.Lock()
		s.statusPort = uint16(allocatedPort)
		s.mutex.Unlock()
	}
	defer l.Close()

	go func() {
		if err := http.Serve(l, mux); err != nil {
			if network.IsUnexpectedListenerError(err) {