example default date with custom value

post.js

// before install  : npm install moment --save


var mongoose    = require('mongoose'),
    moment      = require('moment')
    postSchema  =  new mongoose.Schema({
        createdAt: {
            type: Date,
            default: Date.now
        },
        expiresAt: {
            type: Date,
            default: function(){
              return new Date(moment().add(1, 'month').format());
            }
        }
    });
    
module.exports = mongoose.model('post', postSchema);

please add ',' after moment XD