passport restarting server why code example

Example: passport restarting server why

var session = require('express-session');
var MongoStore = require('connect-mongo')(session);
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/sess');
app.use(express.session({
    secret:'secret',
    maxAge: new Date(Date.now() + 3600000),
    store: new MongoStore(
    // Following lines of code doesn't work
    // with the connect-mongo version 1.2.1(2016-06-20).
    //    {db:mongoose.connection.db},
    //    function(err){
    //        console.log(err || 'connect-mongodb setup ok');
    //   }
    {mongooseConnection:mongoose.connection}
    )        
}));