Extract OAuth logic into a struct

auth/oauth.go

@@ -11,6 +11,18 @@ import (
 	"os/exec"
 )
 
+func main() {
+	oa := OAuthFlow{
+		ClientID:     os.Getenv("GH_OAUTH_CLIENT_ID"),
+		ClientSecret: os.Getenv("GH_OAUTH_CLIENT_SECRET"),
+	}
+	token, err := oa.ObtainAccessToken()
+	if err != nil {
+		panic(err)
+	}
+	fmt.Printf("OAuth access token: %s\n", token)
+}
+
 func randomString(length int) (string, error) {
 	b := make([]byte, length/2)
 	_, err := rand.Read(b)
@@ -20,21 +32,23 @@ func randomString(length int) (string, error) {
 	return fmt.Sprintf("%x", b), nil
 }
 
-func main() {
-	state, _ := randomString(20)
+type OAuthFlow struct {
+	ClientID     string
+	ClientSecret string
+}
 
-	clientID := os.Getenv("GH_OAUTH_CLIENT_ID")
-	clientSecret := os.Getenv("GH_OAUTH_CLIENT_SECRET")
+func (oa *OAuthFlow) ObtainAccessToken() (accessToken string, err error) {
+	state, _ := randomString(20)
 
 	code := ""
 	listener, err := net.Listen("tcp", "localhost:0")
 	if err != nil {
-		panic(err)
+		return
 	}
 	port := listener.Addr().(*net.TCPAddr).Port
 
 	q := url.Values{}
-	q.Set("client_id", clientID)
+	q.Set("client_id", oa.ClientID)
 	q.Set("redirect_uri", fmt.Sprintf("http://localhost:%d", port))
 	q.Set("scope", "repo")
 	q.Set("state", state)
@@ -42,7 +56,7 @@ func main() {
 	cmd := exec.Command("open", fmt.Sprintf("https://github.com/login/oauth/authorize?%s", q.Encode()))
 	err = cmd.Run()
 	if err != nil {
-		panic(err)
+		return
 	}
 
 	http.Serve(listener, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -59,23 +73,24 @@ func main() {
 
 	resp, err := http.PostForm("https://github.com/login/oauth/access_token",
 		url.Values{
-			"client_id":     {clientID},
-			"client_secret": {clientSecret},
+			"client_id":     {oa.ClientID},
+			"client_secret": {oa.ClientSecret},
 			"code":          {code},
 			"state":         {state},
 		})
 	if err != nil {
-		panic(err)
+		return
 	}
 
 	defer resp.Body.Close()
 	body, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
-		panic(err)
+		return
 	}
 	tokenValues, err := url.ParseQuery(string(body))
 	if err != nil {
-		panic(err)
+		return
 	}
-	fmt.Printf("OAuth access token: %s\n", tokenValues.Get("access_token"))
+	accessToken = tokenValues.Get("access_token")
+	return
 }