Small sample app on using goauth2

main.go

// Short example showing how to get an oauth2 token using a .pem key and how the token should be added
// to the http requests.
package main

import (
	"fmt"
	"io/ioutil"
	"net/http"

	"code.google.com/p/goauth2/oauth/jwt"
)

type AuthorizedTransport struct {
	Token     string
	APIKey    string
	Transport http.RoundTripper
}

func (t *AuthorizedTransport) RoundTrip(q *http.Request) (*http.Response, error) {
	q.Header.Set("Authorization", "OAuth "+t.Token)
	args := q.URL.Query()
	args.Add("key", t.APIKey)
	q.URL.RawQuery = args.Encode()
	r, err := t.Transport.RoundTrip(q)
	return r, err
}

// newAuthClient creates an http.Client with OAuth2 authentication.
// key should be the contents of a .pem file, if you have a .p12 key and want to
// convert it to .pem use:
// $ openssl pkcs12 -passin pass:notasecret -in key.p12 -out key.pem -nocerts -nodes
func newAuthClient(email, scope string, key []byte, apiKey string) (*http.Client, error) {
	o, err := jwt.NewToken(email, scope, key).Assert(http.DefaultClient)
	if err != nil {
		return nil, fmt.Errorf("creating auth client: %v", err)
	}
	return &http.Client{Transport: &AuthorizedTransport{o.AccessToken, apiKey, http.DefaultTransport}}, nil
}

func main() {
	key, err := ioutil.ReadFile("key.pem")
	if err != nil {
		panic(err)
	}
	c, err := newAuthClient("campoy@google.com", "https://www.googleapis.com/auth/taskqueue", key, "APIKEY")
	if err != nil {
		panic(err)
	}
	// Authenticated GET request
	res, err := c.Get("www.securedpage.com")
	if err != nil {
		panic(err)
	}
	fmt.Println(res)
}