code: func (srv *Server) Close() error {
  	srv.mu.Lock()
  	defer srv.mu.Unlock()
  	srv.closeDoneChanLocked()
  	err := srv.closeListenersLocked()
  	for c := range srv.conns {
  		c.Close()
  		delete(srv.conns, c)
  	}
  	return err
  }
docs: // Close immediately closes all active listeners and all active
  // connections.
  //
  // Close returns any error returned from closing the Server's
  // underlying Listener(s).