MongoDB connection through mongoose in a Next.js app

mongodb.js

import mongoose from "mongoose";

if (!process.env.MONGODB_URI) {
  throw new Error("Please define the MONGODB_URI environment variable inside .env.local");
}

/**
 * Global is used here to maintain a cached connection across hot reloads
 * in development. This prevents connections growing exponentially
 * during API Route usage.
 */
let cached = global.mongo;

if (!cached) {
  cached = global.mongo = { conn: null, promise: null };
}

export async function connectToDatabase() {
  if (cached.conn) {
    return cached.conn;
  }

  if (!cached.promise) {
    if (mongoose.connection.readyState >= 1) {
      return;
    }
    const opts = {
      useNewUrlParser: true,
      useUnifiedTopology: true,
      useFindAndModify: false,
      useCreateIndex: true,
    };

    cached.promise = mongoose.connect(process.env.MONGODB_URI, opts);
  }
  cached.conn = await cached.promise;
  console.log(cached)
  return cached.conn;
}