got 407 when fetching https with downstream proxy about martian HOT 2 OPEN

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

from martian.

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.

from martian.