Update connection string for updated MongoDB

[mphelps1978]

I know, old repo, older video, but the information is still relevant.

in the connection string on app.js, if you don't append

{useUnifiedTopology: true, useNewUrlParser: true, useCreateIndex: true }

then you will get some deprecation warnings.. New connection string should be:

mongoose.connect('mongodb://localhost/bookstore', {useUnifiedTopology: true, useNewUrlParser: true, useCreateIndex: true });

Versions: Node 10.16.3 Express: 4.17.1 MongoDB: 4.2 Mongoose: 5.8.9