Implement HTTPS requests from client to upstreams

Can now put "https://" in front of Client Address to force it to
use TLS. It doesn't do any verification of the upstream cert. This
is intended to work similarly to the way ngrok does it:

https://ngrok.com/docs#http-local-https

client.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"crypto/tls"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -13,6 +14,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"strings"
 	"sync"
 	"time"
 )
@@ -240,15 +242,35 @@ func (c *BoringProxyClient) BoreTunnel(tunnel Tunnel) context.CancelFunc {
 	return cancelFunc
 }
 
-func (c *BoringProxyClient) handleConnection(conn net.Conn, addr string, port int) {
+func (c *BoringProxyClient) handleConnection(conn net.Conn, upstreamAddr string, port int) {
 
 	defer conn.Close()
 
-	upstreamConn, err := net.Dial("tcp", fmt.Sprintf("%s:%d", addr, port))
+	useTls := false
+	addr := upstreamAddr
+
+	if strings.HasPrefix(upstreamAddr, "https://") {
+		addr = upstreamAddr[len("https://"):]
+		useTls = true
+	}
+
+	var upstreamConn net.Conn
+	var err error
+
+	if useTls {
+		tlsConfig := &tls.Config{
+			InsecureSkipVerify: true,
+		}
+		upstreamConn, err = tls.Dial("tcp", fmt.Sprintf("%s:%d", addr, port), tlsConfig)
+	} else {
+		upstreamConn, err = net.Dial("tcp", fmt.Sprintf("%s:%d", addr, port))
+	}
+
 	if err != nil {
 		log.Print(err)
 		return
 	}
+
 	defer upstreamConn.Close()
 
 	var wg sync.WaitGroup
@@ -260,7 +282,13 @@ func (c *BoringProxyClient) handleConnection(conn net.Conn, addr string, port in
 		if err != nil {
 			log.Println(err.Error())
 		}
-		upstreamConn.(*net.TCPConn).CloseWrite()
+
+		if c, ok := upstreamConn.(*net.TCPConn); ok {
+			c.CloseWrite()
+		} else if c, ok := upstreamConn.(*tls.Conn); ok {
+			c.CloseWrite()
+		}
+
 		wg.Done()
 	}()