code: func (l *Listener) Accept() (net.Conn, error) {
  	select {
  	case <-l.context.Done():
  		return nil, trace.ConnectionProblem(nil, "listener is closed")
  	case conn := <-l.connC:
  		if conn == nil {
  			return nil, trace.ConnectionProblem(nil, "listener is closed")
  		}
  		return conn, nil
  	}
  }
docs: // Accept accepts connections from parent multiplexer listener