Async call to authen Firebase via Meteor

firebase_authen.js

// https://github.com/firebase/firebase-token-generator-node

Meteor.methods({
    enterChat: function (userId) {

        if (!userId) {
            throw new Meteor.Error("not-logged-in",
                "Must be logged in to enter chat.");
        }

        var authWithCustomToken = Meteor.wrapAsync(function (userId, callback) {
            var FirebaseTokenGenerator = Meteor.npmRequire("firebase-token-generator");
            var tokenGenerator = new FirebaseTokenGenerator("YOUR_FIREBASE_SECRET");
            var token = tokenGenerator.createToken({uid: userId});
            console.log("uid : " + userId);
            console.log("token : " + token);

            var Firebase = Meteor.npmRequire("firebase");
            var firebase = new Firebase('https://radiant-fire-foo.firebaseio.com/');

            firebase.authWithCustomToken(token, function (error, authData) {
                callback(error, {response: authData});
            });
        });

        return authWithCustomToken(userId);
    }
});