implement github oauth, set demo to github auth

auth/github/github.go

@@ -1 +1,102 @@
 package github
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"gitlab.127-0-0-1.fr/vx3r/wg-gen-web/model"
+	"golang.org/x/oauth2"
+	oauth2Github "golang.org/x/oauth2/github"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"time"
+)
+
+type Github struct{}
+
+var (
+	oauth2Config *oauth2.Config
+)
+
+// Setup validate provider
+func (o *Github) Setup() error {
+	oauth2Config = &oauth2.Config{
+		ClientID:     os.Getenv("OAUTH2_CLIENT_ID"),
+		ClientSecret: os.Getenv("OAUTH2_CLIENT_SECRET"),
+		RedirectURL:  os.Getenv("OAUTH2_REDIRECT_URL"),
+		Scopes:       []string{"user"},
+		Endpoint:     oauth2Github.Endpoint,
+	}
+
+	return nil
+}
+
+// CodeUrl get url to redirect client for auth
+func (o *Github) CodeUrl(state string) string {
+	return oauth2Config.AuthCodeURL(state)
+}
+
+// Exchange exchange code for Oauth2 token
+func (o *Github) Exchange(code string) (*oauth2.Token, error) {
+	oauth2Token, err := oauth2Config.Exchange(context.TODO(), code)
+	if err != nil {
+		return nil, err
+	}
+
+	return oauth2Token, nil
+}
+
+// UserInfo get token user
+func (o *Github) UserInfo(oauth2Token *oauth2.Token) (*model.User, error) {
+	// https://developer.github.com/apps/building-oauth-apps/authorizing-oauth-apps/
+
+	// we have the token, lets get user information
+	req, err := http.NewRequest("GET", "https://api.github.com/user", nil)
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header.Set("Authorization", fmt.Sprintf("token %s", oauth2Token.AccessToken))
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("http status %s expect 200 OK", resp.Status)
+	}
+
+	bodyBytes, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	var data map[string]interface{}
+	err = json.Unmarshal(bodyBytes, &data)
+	if err != nil {
+		return nil, err
+	}
+
+	// get some infos about user
+	user := &model.User{}
+
+	if val, ok := data["name"]; ok && val != nil {
+		user.Name = val.(string)
+	}
+	if val, ok := data["email"]; ok && val != nil {
+		user.Email = val.(string)
+	}
+	if val, ok := data["html_url"]; ok && val != nil {
+		user.Profile = val.(string)
+	}
+
+	// openid specific
+	user.Sub = "github is not an openid provider"
+	user.Issuer = "https://github.com"
+	user.IssuedAt = time.Now().UTC()
+
+	return user, nil
+}