Express auth app not hangs on form submit

I am trying an Example from Jump start node.js(chapterote 1 Authentication).I wrote all the program and created all the files and folders witch is needed for chapter 1.For those who dont know Chapter 1 is about using mongolab cloud Service.

form.html

<form action="/signup" method="post">
  <div>
    <label>Username:</label>
    <input type="text" name="username"/><br/>
  </div>
  <div>
    <label>Password:</label>
    <input type="password" name="password"/>
  </div>
  <div><input type="submit" value="Sign Up"/></div>
</form>`

lib/db.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
module.exports.mongoose = mongoose;
module.exports.Schema = Schema;
// Connect to cloud database

var username = "user"
var password = "password";
var address = ' @dbh42.mongolab.com:27427/nockmarket';
connect();
// Connect to mongo
function connect() {
  var url = 'mongodb://' + username + ':' + password + address;
  console.log('[*] not reaching here');
  mongoose.connect(url);
}
function disconnect() {mongoose.disconnect()}

models/User.js

var db = require('../lib/db');
var UserSchema = new db.Schema({
  username : {type: String, unique: true}
  , password : String
})
var MyUser = db.mongoose.model('User', UserSchema);
// Exports
module.exports.addUser = addUser;
// Add user to database
function addUser(username, password, callback) {
  var instance = new MyUser();
  instance.username = username;
  instance.password = password;
  instance.save(function (err) {
    if (err) {
      callback(err);
    }
    else {
      callback(null, instance);
    }
  });
}

When I sumbits the form app hangs and its not calling connect() function witch connects to the mongolab it just waits for finish but nothing happens.

thanks,