proxy.go

func (c *Connection) duplexPipe() {
	upstreamChannel := chanFromConnection(c.upstream)
	clientChannel := chanFromConnection(c.client)
	for {
		select {
		case b1 := <-upstreamChannel:
			if b1 == nil {
				return
			} else {
				c.client.Write(b1)
			}
		case b2 := <-clientChannel:
			if b2 == nil {
				return
			} else {
				c.upstream.Write(b2)
			}
		}
	}
}

func chanFromConnection(tcpConnection net.Conn) chan []byte {
	channel := make(chan []byte)
	go func() {
		b := make([]byte, 2<<10) 
		for {
			n, err := tcpConnection.Read(b)  // --- blocking operation ---
			if n > 0 {
				res := make([]byte, n)
				copy(res, b[:n])
				channel <- res
			}
			if err != nil {
				close(channel)
				return
			}
		}
	}()
	return channel
}