got 407 when fetching https with downstream proxy

[skiloop]

My remote proxy which is password protected and supports https, when applies to martian as downstream proxy, 407 is got.

martian -addr=:8000 -api martian -organization Martian -downstream-proxy-url http://xxxx:password@someproxy:60000

curl -x http://localhost:8000 https://ip.cn  -v

then comes the following result:

• Rebuilt URL to: https://ip.cn/
• Trying ::1...
• TCP_NODELAY set
• Connected to localhost (::1) port 8000 (#0)
• allocate connect buffer!
• Establish HTTP proxy tunnel to ip.cn:443

CONNECT ip.cn:443 HTTP/1.1
Host: ip.cn:443
User-Agent: curl/7.59.0
Proxy-Connection: Keep-Alive

< HTTP/1.1 407 Proxy Authentication Required
< Connection: close
< Content-Type: text/html
< Server: someproxy
<

• Received HTTP code 407 from proxy after CONNECT
• CONNECT phase completed!
• Closing connection 0
  curl: (56) Received HTTP code 407 from proxy after CONNECT

[skiloop]

after monitor network traffic, I found not Proxy-Authorization in headers fields of the CONNECT method to downstream proxy.
I changed a few lines of function Proxy.connect to:

		pbw := bufio.NewWriter(conn)
		pbr := bufio.NewReader(conn)
		if p.proxyURL.User != nil {
			req.Header.Add("Proxy-Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(p.proxyURL.User.String())))
		}
		req.Write(pbw)
		pbw.Flush()

and this results stucking at tls handshakes

[skiloop]

The problem may be the usage of http.ReadResponse for CONNECT

res, err := http.ReadResponse(pbr, req)

When it write response back, "Connection: close" is added automatically.