google

ctx := appengine.NewContext(nil)
opts, err := oauth2.New(
	google.AppEngineContext(ctx),
	oauth2.Scope(
		"https://www.googleapis.com/auth/bigquery",
		"https://www.googleapis.com/auth/blogger",
	),
)
if err != nil {
	log.Fatal(err)
}
// The following client will be authorized by the App Engine
// app's service account for the provided scopes.
client := http.Client{Transport: opts.NewTransport()}
client.Get("...")

Output:

opts, err := oauth2.New(
	// Query Google Compute Engine's metadata server to retrieve
	// an access token for the provided account.
	// If no account is specified, "default" is used.
	google.ComputeEngineAccount(""),
)
if err != nil {
	log.Fatal(err)
}
client := http.Client{Transport: opts.NewTransport()}
client.Get("...")

Output:

// Your credentials should be obtained from the Google
// Developer Console (https://console.developers.google.com).
opts, err := oauth2.New(
	// The contents of your RSA private key or your PEM file
	// that contains a private key.
	// If you have a p12 file instead, you
	// can use `openssl` to export the private key into a pem file.
	//
	//    $ openssl pkcs12 -in key.p12 -out key.pem -nodes
	//
	// It only supports PEM containers with no passphrase.
	oauth2.JWTClient(
		"xxx@developer.gserviceaccount.com",
		[]byte("-----BEGIN RSA PRIVATE KEY-----...")),
	oauth2.Scope(
		"https://www.googleapis.com/auth/bigquery",
		"https://www.googleapis.com/auth/blogger",
	),
	google.JWTEndpoint(),
	// If you would like to impersonate a user, you can
	// create a transport with a subject. The following GET
	// request will be made on the behalf of user@example.com.
	// Subject is optional.
	oauth2.Subject("user@example.com"),
)
if err != nil {
	log.Fatal(err)
}

// Initiate an http.Client, the following GET request will be
// authorized and authenticated on the behalf of user@example.com.
client := http.Client{Transport: opts.NewTransport()}
client.Get("...")

Output:

// Your credentials should be obtained from the Google
// Developer Console (https://console.developers.google.com).
// Navigate to your project, then see the "Credentials" page
// under "APIs & Auth".
// To create a service account client, click "Create new Client ID",
// select "Service Account", and click "Create Client ID". A JSON
// key file will then be downloaded to your computer.
opts, err := oauth2.New(
	google.ServiceAccountJSONKey("/path/to/your-project-key.json"),
	oauth2.Scope(
		"https://www.googleapis.com/auth/bigquery",
		"https://www.googleapis.com/auth/blogger",
	),
)
if err != nil {
	log.Fatal(err)
}
// Initiate an http.Client. The following GET request will be
// authorized and authenticated on the behalf of
// your service account.
client := http.Client{Transport: opts.NewTransport()}
client.Get("...")

Output:

// Your credentials should be obtained from the Google
// Developer Console (https://console.developers.google.com).
opts, err := oauth2.New(
	oauth2.Client("YOUR_CLIENT_ID", "YOUR_CLIENT_SECRET"),
	oauth2.RedirectURL("YOUR_REDIRECT_URL"),
	oauth2.Scope(
		"https://www.googleapis.com/auth/bigquery",
		"https://www.googleapis.com/auth/blogger",
	),
	google.Endpoint(),
)
if err != nil {
	log.Fatal(err)
}
// Redirect user to Google's consent page to ask for permission
// for the scopes specified above.
url := opts.AuthCodeURL("state", "online", "auto")
fmt.Printf("Visit the URL for the auth dialog: %v", url)

// Handle the exchange code to initiate a transport
t, err := opts.NewTransportFromCode("exchange-code")
if err != nil {
	log.Fatal(err)
}
client := http.Client{Transport: t}
client.Get("...")

Output: