text: 
  var db = require('./mysql');
  
   var user = {
  
           id: { type: 'serial', key: true } , //主键
           username: String,
           password: String,
           created_at  : {type: 'integer',defaultValue: 0 },
           updated_at  : {type: 'integer',defaultValue: 0}
   };
  var User = db.define('user',user);
  
  module.exports = User;