events.js:141
      throw er; // Unhandled 'error' event
MongoError: connection 0 to localhost:27017 timed out
at Function.MongoError.create (/home/ubuntu/scripts/node_modules/mongodb-core/lib/error.js:29:11)
    at Socket.<anonymous> (/home/ubuntu/scripts/node_modules/mongodb-core/lib/connection/connection.js:184:20)
    at Socket.g (events.js:260:16)
    at emitNone (events.js:67:13)
    at Socket.emit (events.js:166:7)
    at Socket._onTimeout (net.js:318:8)
    at _runOnTimeout (timers.js:524:11)
    at _makeTimerTimeout (timers.js:515:3)
    at Timer.unrefTimeout (timers.js:584:5)

var mongoose = require('mongoose');
var option = {
    server: {
        socketOptions: {
            keepAlive: 300000,
            connectTimeoutMS: 30000
        }
    },
    replset: {
        socketOptions: {
            keepAlive: 300000,
            connectTimeoutMS: 30000
        }
    }
};

var mongoURI = process.env.MONGODB_URI;
mongoose.connect(mongoURI, option).then(function(){
    //connected successfully
}, function(err) {
    //err handle
});