net_transport.go
func (n *NetworkTransport) Close() error {
	n.shutdownLock.Lock()
	defer n.shutdownLock.Unlock()

	if !n.shutdown {
		close(n.shutdownCh)
		n.stream.Close()
		n.shutdown = true
	}
	return nil
}
func (n *NetworkTransport) Close() error {
	n.shutdownLock.Lock()
	defer n.shutdownLock.Unlock()

	if !n.shutdown {
		close(n.shutdownCh)
		n.stream.Close()
		n.shutdown = true
	}
	return nil
}
// Close is used to stop the network transport.