defer m.respMu.Unlock()
	m.closeLocked()
}

func (m *muxClient) closeLocked() {
	if m.closed {
		return
	}
	// We hold the lock, so nobody can modify m.respWait while we're closing.
	if m.respWait != nil {
		xioutil.SafeClose(m.respWait)
		m.respWait = nil
	}
	m.closed = true