I am learning to use Mongoose with NextJS and I keep running into this error. I have looked over similar questions but didn't figure out how to solve this. I have followed a tutorial video for implementing Mongoose step by step but in the video this problem didn't occur. Also, I hate to say it this inaccurately but it only happens "sometimes". Seems like every time I run the server first POST request always goes through, GET requests are also fine but when I try multiple POST requests it occurs. After restarting the server it works again. Here is my code:

import mongoose from "mongoose"

const connection = {}

async function dbConnect() {
    if (connection.isConnected) {
        retrun
    }

    const db = await mongoose.connect(process.env.MONGO_URI, {
        useNewUrlParser: true,
        useUnifiedTopology: true,
    })

    connection.isConnected = db.connections[0].readyState
    console.log(connection.isConnected)

}

export default dbConnect

const mongoose = require("mongoose")

let NoteSchema = new mongoose.Schema({
    email: {
        type: String,
        required: [true, "Please enter your email"]
    }
})

module.exports = mongoose.model.Note || mongoose.model("Note", NoteSchema);

import dbConnect from "../../utils/dbConnect"
import Note from "../../models/Note"

dbConnect()

export default async (req, res) => {
    const { method } = req

    switch(method) {
        case "GET":
            try {
                const notes = await Note.find({})

                res.status(200).json({ success: true, data: notes })
            } catch (error) {
                res.status(400).json({ success: false })
            }
            break
        case "POST":
            try {
                const note = await Note.create(req.body)

                res.status(201).json({ success: true, data: note })
            } catch (error) {
                res.status(400).json({ success:false })
            }
            break
        default:
            res.status(400).json({ success:false })
            break
    }
}

Thanks for any help.