passport restarting server why

1var session = require('express-session');
2var MongoStore = require('connect-mongo')(session);
3var mongoose = require('mongoose');
4mongoose.connect('mongodb://localhost/sess');
5app.use(express.session({
6    secret:'secret',
7    maxAge: new Date(Date.now() + 3600000),
8    store: new MongoStore(
9    // Following lines of code doesn't work
10    // with the connect-mongo version 1.2.1(2016-06-20).
11    //    {db:mongoose.connection.db},
12    //    function(err){
13    //        console.log(err || 'connect-mongodb setup ok');
14    //   }
15    {mongooseConnection:mongoose.connection}
16    )        
17}));