Wrapping app.route with MongoClient.connect()

This is my app.route for .get, & .post. Rather than repeat the MongoClient.connect for each function I want to wrap the app.route with it instead. But it doesn’t seem to work.
Can anyone explain where I am going wrong?

module.exports = function (app) {
MongoClient.connect(MONGODB_CONNECTION_STRING, {useNewUrlParser: true,  useUnifiedTopology: true}, function(err, db) {
    .get(function (req, res) {  
      db.collection('books').find({}).toArray ((err, docs) => {
        if(docs) {
          console.log(docs); //nothing is consoled
        } else {
          console.log("no docs"); //nothing is consoled
    .post(function (req, res){  })