MongoDB 3.0 and mongoDB 2.2

I create NodeJS V8 app and use mongoDB local server.

I had mongoDB version ^2.2.34 and connect to DB

    let mongodb = require('mongodb');
    let mongoClient = mongodb.MongoClient;

    let connection = mongoClient.connect('mongodb://localhost:27017/Test');

    let getCollection = function (c) {
        return connection.then(function (db) {
            return db.collection(c);
        });
    };

It worked. I update my mongoDB version to ^3.0.1 and have error

(node:16320) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: db.collection is not a function

Why in new version it isn't work and how I can change code?

Copyright Notice：Content Author:「Aksenov Vladimir」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/48464522/mongodb-3-0-and-mongodb-2-2