func (m *muxServer) close() {
	m.cancel()
	m.recvMu.Lock()
	defer m.recvMu.Unlock()

	if m.inbound != nil {
		xioutil.SafeClose(m.inbound)
		m.inbound = nil
	}

	if m.outBlock != nil {
		xioutil.SafeClose(m.outBlock)
		m.outBlock = nil
	}