dns_client.go

package main

import (
	"fmt"
	"os"

	"github.com/miekg/dns"
	"strings"
)

func main() {
	client := &dns.Client{}
	message := &dns.Msg{}
	message.SetQuestion(os.Args[1] + ".", dns.TypeCNAME)
	message.RecursionDesired = true

	config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
	r, _, err := client.Exchange(message, config.Servers[0]+":"+config.Port)
	if err != nil {
		panic(err)
	}
	if r.Rcode != dns.RcodeSuccess {
		panic(r.Rcode)
	}
	for _, a := range r.Answer {
		if cname, ok := a.(*dns.CNAME); ok {
			fmt.Printf("%s\n", cname.String())
			if strings.Contains(cname.String(), "custom-domain.amebaowndme.com") {
				fmt.Println("OK!")
			}
		}
	}
}