Request and save an Google oAuth2 request_token (node.js, express)

gistfile1.js

var express = require( 'express' )
  , OAuth2 = require( 'oauth' ).OAuth2
  , querystring = require( 'querystring' )
  , request = require( 'request' )
  , fs = require('fs');

var oa2;
var app = express.createServer();
app.use(express.logger());
app.use(express.bodyParser());
app.use(express.cookieParser());
app.use(express.session({
	secret: "secret"
}));

app.get('/', function(req, res) {
	
	oa2.getOAuthAccessToken( req.query[ 'code' ], { grant_type: 'authorization_code', redirect_uri: 'http://localhost:9004' }, function( error, access_token, refresh_token, results ) {
		if ( !error ) {
			
			fs.writeFile( './token/refresh_token', refresh_token, function( err ) {
				if(err) {
					console.log( err );
				}
				else {
					console.log( 'Refresh token saved!' );
				}
			});
		}
	});
	
});

app.get('/google_login', function(req, res) {
	var getRequestTokenUrl = '';

	oa2 = new OAuth2(
	    'clientId'
	  , 'clientSecret'
	  , 'https://accounts.google.com'
	  , '/o/oauth2/auth'
	  , '/o/oauth2/token'
	);

	var params = {
	  , 'response_type': 'code'
	  , 'scope': 'https://www.googleapis.com/auth/calendar'
	  , 'redirect_uri': 'http://localhost:9004'
	}

	redirectUrl = oa2.getAuthorizeUrl( params );
	res.redirect( redirectUrl );

});

app.listen(9004);
console.log("listening on http://localhost:9004");