MongoDB connection with Next js 

In model folder create a file user.js

for schema

import mongoose from 'mongoose'

const UserSchema = new mongoose.Schema({

  name: String,

  email: String

})

module.exports = mongoose.models.User || mongoose.model('User', UserSchema)

create a file in root lib. MongoDB.js

import mongoose from 'mongoose'

const MONGODB_URI = "mongodb://localhost:27017"

if (!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.mongoose

if (!cached) {

  cached = global.mongoose = { conn: null, promise: null }

}

async function dbConnect () {

  if (cached.conn) {

    return cached.conn

  }

  if (!cached.promise) {

    const opts = {

      useNewUrlParser: true,

      useUnifiedTopology: true,

      bufferCommands: false,

      bufferMaxEntries: 0,

      useFindAndModify: true,

      useCreateIndex: true

    }

    cached.promise = mongoose.connect(MONGODB_URI, opts).then(mongoose => {

      return mongoose

    })

  }

  cached.conn = await cached.promise

  return cached.conn

}

export default dbConnect

in API folder 

import User from '../../models/User'

export default async function handler (req, res) {

  const { method } = req

  await dbConnect()

  switch (method) {

    case 'GET':

      try {

        const users = await User.find({})

        res.status(200).json({ success: true, data: users })

      } catch (error) {

        res.status(400).json({ success: false })

      }

      break

    case 'POST':

      try {

        const user = await User.create(req.body)

        res.status(201).json({ success: true, data: user })

      } catch (error) {

        res.status(400).json({ success: false })

      }

      break

    default:

      res.status(400).json({ success: false })

      break

  }

}