mongoldb-setup.js

class DB {
  private _connection: MongoClient;
	private _db: Db;
	constructor() {}
	public async connect() {
		const mongoClientPromise = MongoClient.connect(process.env.MONGODB_URI, { useNewUrlParser: true, useUnifiedTopology: true });

		this._connection = await mongoClientPromise;
		this._db = this._connection.db(process.env.MONGODB_NAME);
	}
}