update-dns/main.go

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"

	"github.com/pkg/errors"
	"github.com/urfave/cli"
)

func main() {
	app := cli.NewApp()
	app.Name = "update-dns"
	app.Usage = "update dnsimple with public ip address"
	app.Action = action

	app.Flags = []cli.Flag{
		cli.StringFlag{
			Name:  "url",
			Value: "https://whatismyipv6.buddy.wtf/json",
			Usage: "url to use to get public ip address",
		},
	}

	app.Run(os.Args)
}

func action(context *cli.Context) error {
	result, err := getIP(context.String("url"))
	if err != nil {
		return errors.Wrap(err, "could not get IP address")
	}
	fmt.Println(result.IP)
	return nil
}

type whatIsMyIPResult struct {
	IP      string `json:ip`
	Version string `json:version`
}

func getIP(url string) (*whatIsMyIPResult, error) {
	result, err := http.Get(url)
	if err != nil {
		return nil, errors.Wrap(err, "could not get url "+url)
	}
	defer result.Body.Close()
	ipResult := &whatIsMyIPResult{}
	if err := json.NewDecoder(result.Body).Decode(ipResult); err != nil {
		return nil, errors.Wrap(err, "could parse json from url "+url)
	}
	return ipResult, nil
}