DNS test

dnstest.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net"
	"os"
	"path/filepath"
	"time"
)

func main() {
	sleep := flag.String("wait", "1s", "wait time between attempts")
	flag.Parse()

	rest := flag.Args()
	if len(rest) == 0 {
		fmt.Printf("usage: %s <host>\n", filepath.Base(os.Args[0]))
		return
	}
	host := rest[0]

	sleepTime, err := time.ParseDuration(*sleep)
	if err != nil {
		fmt.Printf("cannot parse duration: %v\n", err)
		return
	}

	for {
		addrs, err := net.LookupHost(host)
		if err != nil {
			log.Printf("failed: %v\n", err)
		} else {
			log.Printf("resolved: %v\n", addrs)
		}
		time.Sleep(sleepTime)
	}

}

go build dnstest.go
GODEBUG=netdns=cgo+2 ./dnstest -wait 0.5s google.com

https://asciinema.org/a/9mxxvwdweipbty7t9v8ui4k0w