A Go Proxy which can help resolve local .xip.io address

XipIoProxy.go

package main

import (
	"flag"
	"github.com/elazarl/goproxy"
	"log"
	"net"
	"net/http"
	"regexp"
	"strings"
)

// address should be "host:port" format
func resolveXipIoAddr(addr string) string {
	host, port, err := net.SplitHostPort(addr)
	if err != nil {
		return addr
	}
	if strings.HasSuffix(host, "xip.io") {
		fields := strings.Split(host, ".")
		if sz := len(fields); sz >= 6 {
			i := sz - 6
			j := sz - 2
			host = strings.Join(fields[i:j], ".")
		}
	}
	addr = host + ":" + port
	return addr
}

func xipEnabledDial(network, addr string) (c net.Conn, err error) {
	addr = resolveXipIoAddr(addr)
	addri, err := net.ResolveTCPAddr("tcp", addr)
	if err != nil {
		return nil, err
	}
	return net.DialTCP("tcp", nil, addri)
}

func main() {
	verbose := flag.Bool("v", false, "should every proxy request be logged to stdout")
	addr := flag.String("addr", ":8080", "proxy listen address")
	flag.Parse()
	proxy := goproxy.NewProxyHttpServer()
	// for https request
	proxy.OnRequest(goproxy.ReqHostMatches(regexp.MustCompile("^.*xip.io:443$"))).
		HandleConnect(goproxy.AlwaysMitm)
	// use customized dial 
	proxy.Tr.Dial = xipEnabledDial
	proxy.Verbose = *verbose
	log.Fatal(http.ListenAndServe(*addr, proxy))
}