Simple Google Login

This is a work in progress.

I got tired of baroque libraries that pull inn all manner of unwanted cruft so I made a bare bones library to log in using Google. This code takes care of only the Google login.

Import the following package

"github.com/borud/gin/pkg/auth"

Abbreviated example

Here is an abbreviated example of how to use this module. The loginCallback is where you would create the session etc, but since people use different libraries for handling sessions we leave this part up to you.

package main

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

	"github.com/borud/gin/pkg/auth"
)

func main() {
	googleAuth := auth.New(&auth.GoogleAuthConfig{
		ClientID:      os.Getenv("GOOGLE_CLIENT_ID"),
		ClientSecret:  os.Getenv("GOOGLE_CLIENT_SECRET"),
		CallbackURL:   "http://localhost:3000/google/callback",
		LoginCallback: loginCallback,
	})

	http.HandleFunc("/google/login", googleAuth.GoogleLoginHandler)
	http.HandleFunc("/google/callback", googleAuth.GoogleCallbackHandler)
	http.ListenAndServe(":3000", nil)
}

func loginCallback(w http.ResponseWriter, r *http.Request, userinfo *auth.Userinfo) {
	html := `Hello %s<p><img src="%s"`
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	fmt.Fprintf(w, html, userinfo.Name, userinfo.Picture)
}

Please see the example.go file for a more complete example.

Session management

You have to do your own session creation and management. You can do this by implementing your own callback of the following type:

type LoginFunc func(w http.ResponseWriter, r *http.Request, u *Userinfo)

The Userinfo struct that is provided contains the following fields:

type Userinfo struct {
	ID            string `json:"id"`
	Email         string `json:"email"`
	VerifiedEmail bool   `json:"verified_email"`
	Name          string `json:"name"`
	GivenName     string `json:"given_name"`
	FamilyName    string `json:"family_name"`
	Picture       string `json:"picture"`
	Locale        string `json:"locale"`
	HostDomain    string `json:"hd"`
}

Providing credentials

This assumes you have your credentials in the environment, so make sure you have the following environment variables set.

GOOGLE_CLIENT_ID=<your client id>
GOOGLE_CLIENT_SECRET=<your client secret>

You can create your client credentials at: https://console.developers.google.com/apis/credentials