server/server.js

server.js

const mongoose = require('mongoose');

// use body parser to get data from POST requests
...

// Use API routes from the api folder
...

// Connect to Mongo
mongoose.connect(process.env.DB, {
    useNewUrlParser: true,
    useUnifiedTopology: true
}).then(() => console.log('MongoDB Connected...')).catch(err => console.log(err));

app.listen(...);