passport google only saveone account in first time

I'm use passport-google to login , but it only save one account in first time I login . When I try login with different account , it not save in database . Here is my code

router

var GoogleStrategy = require('passport-google-oauth').OAuth2Strategy;
        passport.use(new GoogleStrategy({
    clientID: 'xxx',
    clientSecret: 'xxx',
    callbackURL: "http://localhost:2912/auth/google/callback"
  },
  function(accessToken, refreshToken, profile, done) {
        User.findOne({'google.id':profile.id},function(err,user) {
                    if(err) 
                        return done(err);
                    if(user){
                        return done(null,user);
                    }else{
                        var newUser = new User();
                        newUser.google.id = profile.id;
                        newUser.google.token = accessToken;
                        newUser.google.name  = profile.displayName;
                        newUser.google.email = profile.emails[0].value;
                        newUser.save(function(err) {
                            if(err)
                                 console.log(err);
                            return done(null,newUser);
                        })
                    }
                });
  }
));
app.get('/auth/google',
  passport.authenticate('google', {scope : ['profile', 'email']  }));

app.get('/auth/google/callback', 
  passport.authenticate('google', { failureRedirect: '/login' }),
  function(req, res) {
    res.redirect('/');
  });

model

var userSchema = new Schema({


    google:{
        id:String,
        token:String,
        email:String,
        name:String
    }
});

Where is my wrong? Please help me . Any help would be appreciated

via Thanh Tùng