collection.ensureIndex is deprecated

mongoose.set('useCreateIndex', true);mongoose.connect(dbURI, {
    useNewUrlParser: true,
    useUnifiedTopology: true,
    useCreateIndex: true,
    useFindAndModify: true,
})mongoose.set('useNewUrlParser', true);
mongoose.set('useFindAndModify', false);
mongoose.set('useCreateIndex', true);