code: func (t *TcpTransport) Listen(laddr ma.Multiaddr) (tpt.Listener, error) {
  	list, err := t.maListen(laddr)
  	if err != nil {
  		return nil, err
  	}
  	list = &lingerListener{list, 0}
  	return t.Upgrader.UpgradeListener(t, list), nil
  }
docs: // Listen listens on the given multiaddr.