Node.js + googleapis to query google analytics

googleAnalytics.js

var googleapis = require('googleapis'),
	JWT = googleapis.auth.JWT,
	analytics = googleapis.analytics('v3');

var SERVICE_ACCOUNT_EMAIL = 'XXXXXXXXXX@developer.gserviceaccount.com';
var SERVICE_ACCOUNT_KEY_FILE = __dirname + '/key.pem';


var authClient = new JWT(
	SERVICE_ACCOUNT_EMAIL,
	SERVICE_ACCOUNT_KEY_FILE,
	null,
	['https://www.googleapis.com/auth/analytics.readonly']
);

authClient.authorize(function(err, tokens) {
	if (err) {
		console.log(err);
		return;
	}

	analytics.data.ga.get({ 
		auth: authClient,
		'ids': 'ga:XXXXXXXX',
		'start-date': '2015-01-19',
		'end-date': '2015-01-19',
		'metrics': 'ga:visits'
	}, function(err, result) {
		console.log(err);
		console.log(result);
	});
});