manually create conn with an http proxy in go

http.go

func (p *Proxy) GetHttpImapConnection(imapServer string) (net.Conn, error) {
	proxyAddr := p.IpAddress + ":" + strconv.Itoa(p.Port)
	conn, err := net.Dial("tcp", proxyAddr)
	if err != nil {
		return nil, err
	}

	request := "CONNECT " + imapServer + " HTTP/1.1\r\nHost: " + imapServer + "\r\n"
	if p.HasCredentials() {
		credentials := p.GetEncodedCredentials()
		request += "Proxy-Authorization: Basic " + credentials + "\r\n\r\n"
	}

	_, err = conn.Write([]byte(request))
	if err != nil {
		conn.Close()
		return nil, err
	}

	response, err := bufio.NewReader(conn).ReadString('\n')
	if err != nil {
		conn.Close()
		return nil, err
	}

	if response[:12] != "HTTP/1.1 200" {
		conn.Close()
		return nil, errors.New("proxy connection failed: " + response)
	}

	conn = tls.Client(conn, &tls.Config{InsecureSkipVerify: true})
	return conn, nil
}