put models in file not schema

db/booker.js

@@ -0,0 +1,14 @@
+import * as mongoose from 'mongoose'
+
+const BookerSchema = new mongoose.Schema(
+  {
+    name: { type: String, required: true },
+    email: { type: String, required: true, unique: true, minlength: 5 },
+    street: { type: String, required: true },
+    zip: { type: String, required: true },
+    city: { type: String, required: true },
+  },
+  { timestamps: true }
+)
+
+export default mongoose.models.Booker || mongoose.model('Booker', BookerSchema)

db/booking.js

@@ -1,21 +1,14 @@
-import { Schema } from 'mongoose'
+import * as mongoose from 'mongoose'
 
 import { getDays, dateFormat } from '../helpers/date'
 
-export const BookerSchema = new Schema(
+const BookingSchema = new mongoose.Schema(
   {
-    name: { type: String, required: true },
-    email: { type: String, required: true, unique: true, minlength: 5 },
-    street: { type: String, required: true },
-    zip: { type: String, required: true },
-    city: { type: String, required: true },
-  },
-  { timestamps: true }
-)
-
-export const BookingSchema = new Schema(
-  {
-    booker: { type: Schema.Types.ObjectId, ref: 'Booker', required: true },
+    booker: {
+      type: mongoose.Schema.Types.ObjectId,
+      ref: 'Booker',
+      required: true,
+    },
     startDate: {
       type: Date,
       required: true,
@@ -43,3 +36,6 @@ export const BookingSchema = new Schema(
 BookingSchema.virtual('days').get(function () {
   return getDays({ startDate: this.startDate, endDate: this.endDate })
 })
+
+export default mongoose.models.Booking ||
+  mongoose.model('Booking', BookingSchema)

db/index.js

@@ -1,24 +1,25 @@
-import mongoose from 'mongoose'
-import { BookingSchema, BookerSchema } from './schema'
+import * as mongoose from 'mongoose'
 
-mongoose.connect(process.env.MONGO_URI, {
-  useNewUrlParser: true,
-  useUnifiedTopology: true,
-  connectTimeoutMS: 1000,
-  serverSelectionTimeoutMS: 5000,
-})
+import Booker from './booker'
+import Booking from './booking'
 
-if (process.env.NODE_ENV !== 'production') {
-  mongoose.modelNames().includes('Booker') && mongoose.deleteModel('Booker')
-  mongoose.modelNames().includes('Booking') && mongoose.deleteModel('Booking')
+let connectedPromise
+
+function connect() {
+  if (connectedPromise) {
+    return
+  }
+
+  connectedPromise = mongoose.connect(process.env.MONGO_URI, {
+    useNewUrlParser: true,
+  })
+
+  return connectedPromise
 }
 
-export const Booker =
-  mongoose.models.Booker || mongoose.model('Booker', BookerSchema)
-export const Booking =
-  mongoose.models.Booking || mongoose.model('Booking', BookingSchema)
-
 export async function getBookedDays() {
+  await connect()
+
   const bookings = await Booking.find(
     {
       status: { $ne: 'rejected' },
@@ -48,6 +49,7 @@ export async function createBooking({
   zip,
   city,
 }) {
+  await connect()
   const booking = new Booking({ startDate, endDate, purpose, org, destination })
   const bookedDays = await getBookedDays()