refactor: move init github client

cmd/update-go-mod/main.go

@@ -18,10 +18,18 @@ const (
 )
 
 func main() {
-	// Prepare GitHub
-	var ghClient *github.Client
+	app := cli.NewApp(
+		initGitHubClient(),
+	)
+	app.Run()
+}
+
+func initGitHubClient() *github.Client {
 	netrcData, err := netrc.ParseFile(netrcPath)
-	if err == nil {
+	if err != nil {
+		return nil
+	}
+
 	var ghAccessToken string
 	for _, machine := range netrcData.Machines {
 		if machine.Name == netrcMachineGitHub {
@@ -30,17 +38,17 @@ func main() {
 		}
 	}
 
-		if ghAccessToken != "" {
+	if ghAccessToken == "" {
+		return nil
+	}
+
 	ghTokenSrc := oauth2.StaticTokenSource(
 		&oauth2.Token{
 			AccessToken: strings.TrimSpace(ghAccessToken),
 		},
 	)
 	ghHTTPClient := oauth2.NewClient(context.Background(), ghTokenSrc)
-			ghClient = github.NewClient(ghHTTPClient)
-		}
-	}
+	ghClient := github.NewClient(ghHTTPClient)
 
-	app := cli.NewApp(ghClient)
-	app.Run()
+	return ghClient
 }