Heroku + MongoLab插件与Node.js应用程序连接错误 - 错误：连接ECONNREFUSED 127.0.0.1:27017

When trying to start Node.js app hosted on Heroku with MongoLab addons, I got the following error on Heroku logs when connecting to MongoDB. It looks like it is trying to connect to a local mongo even though I already set the heroku environment variable.When trying to start Node.js app hosted on Hero