Node Express MongoDB Native驱动程序 - 在哪里打开数据库连接？

I want to open and initialise the DB via Node-Mongo-Native-Driver once in the app.js file and then leave it open and do reads in the routes. I put following code in the app.js and wrapping the app.gets in order to made them available when the DB is opened:I want to open and initialise the DB via Node-M