Basic OAuth with goth in golang.

goth_auth.go

package main

import (
	"flag"
	"fmt"
	"net/http"

	"github.com/gorilla/mux"
	"github.com/markbates/goth"
	"github.com/markbates/goth/gothic"
	"github.com/markbates/goth/providers/facebook"
	"github.com/markbates/goth/providers/gplus"
	"github.com/markbates/goth/providers/twitter"
)

var (
	twitterKey     = flag.String("twitter_key", "", "this is your twitter API key")
	twitterSecret  = flag.String("twitter_secret", "", "this is your twitter secre")
	facebookKey    = flag.String("facebook_key", "", "this is your facebook API key")
	facebookSecret = flag.String("facebook_secret", "", "this is your facebook API secret")
	gplusKey       = flag.String("gplus_key", "", "this is your gplus API key")
	gplusSecret    = flag.String("gplus_secret", "", "this is your gplus API secret")
)

func main() {
	flag.Parse()

	goth.UseProviders(
		twitter.New(*twitterKey, *twitterSecret, "http://localhost:8888/auth/twitter/callback?provider=twitter"),
		facebook.New(*facebookKey, *facebookSecret, "http://localhost:8888/auth/twitter/callback?provider=facebook"),
		gplus.New(*gplusKey, *gplusSecret, "http://localhost:8888/auth/gplus/callback?provider=gplus"),
	)

	gothic.GetState = func(r *http.Request) string {
		return r.URL.Query().Get("state")
	}

	r := mux.NewRouter()
	r.HandleFunc("/auth/{provider}/callback", func(w http.ResponseWriter, r *http.Request) {
		fmt.Println(gothic.GetState(r))
		user, err := gothic.CompleteUserAuth(w, r)
		if err != nil {
			panic(err)
		}

		fmt.Fprintln(w, "logged in!", user)
	})

	r.HandleFunc("/auth/{provider}", gothic.BeginAuthHandler)
	r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "<p><a href='/auth/twitter?provider=twitter'>Click to log in with twitter</a></p>")
		fmt.Fprintf(w, "<p><a href='/auth/facebook?provider=facebook'>Click to log in with facebook</a></p>")
		fmt.Fprintf(w, "<p><a href='/auth/gplus?provider=gplus'>Click to log in with gplus</a></p>")
	})

	http.ListenAndServe("localhost:8888", r)
}