title: MongoServerError: bad auth : Authentication
body: <p>Hi im making an app with node js, mongo db and im deploying in vercel, so i made the aplication and i tested on mode dev and was okay but when execute the comand &quot;now&quot; and see the site it appear a error 500 and im seein from vercel and
  <a href="https://i.stack.imgur.com/nTA9h.png" rel="nofollow noreferrer">the page of vercel function log</a></p>
  <p>it say that bad auth but i tried that on mode dev, so i dont know why is the problem, this is the index.json when i connect</p>
  <pre><code>const express =require('express')
  const mongoose =require('mongoose')
  const bodyParser= require('body-parser')
  const cors= require('cors')
  const meals=require('./routes/meals')
  const orders=require('./routes/order')
  
  const app=express()
  app.use(bodyParser.json())
  app.use(cors())
  mongoose.connect(process.env.MONGODB_URI)
  
  
  
  app.use('/api/meals',meals)
  app.use('/api/order',orders)
  
  
  module.exports=app;
  </code></pre>
  <p>and i created a file .env and i put this</p>
  <p>MONGODB_URI=mongodb+srv://almuerzimaster:GaoJs66Hbj8cLNX5@cluster0.uiie0.mongodb.net/myFirstDatabase?retryWrites=true&amp;w=majority</p>