Wrap errors and use cli library

main.go

@@ -3,16 +3,37 @@ package main
 import (
 	"encoding/json"
 	"fmt"
-	"log"
 	"net/http"
+	"os"
+
+	"github.com/pkg/errors"
+	"github.com/urfave/cli"
 )
 
 func main() {
-	result, err := getIP("https://whatismyipv6.buddy.wtf/json")
+	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 {
-		log.Fatal(err)
+		return errors.Wrap(err, "could not get IP address")
 	}
 	fmt.Println(result.IP)
+	return nil
 }
 
 type whatIsMyIPResult struct {
@@ -23,12 +44,12 @@ type whatIsMyIPResult struct {
 func getIP(url string) (*whatIsMyIPResult, error) {
 	result, err := http.Get(url)
 	if err != nil {
-		return nil, err
+		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, err
+		return nil, errors.Wrap(err, "could parse json from url "+url)
 	}
 	return ipResult, nil
 }