FIXED, the names of the folders in my pc changed when uploaded to github

So, my app looks something like this

├── config
|    ├── app.js
|
└── index.js

app.js

Here i have all my env variables, so I have a central point from which to extract them

require('dotenv').config()

module.exports = {
    appPort: process.env.PORT,
    appUrl: process.env.APP_URL,
    appKey: process.env.APP_KEY,
    frontendUrl: process.env.FRONTEND_URL
}

index.js

central file of the server

const express = require('express')
const cors = require('cors')
const app = express()

const { appPort, frontendUrl } = require('./config/app')

app.listen(appPort , () => {
    console.log(`Server listening on port ${appPort}`);
})

The problem here is that when i deploy it and starts the server, it throws me error

node:internal/modules/cjs/loader:936
   throw err;
   ^
 
 Error: Cannot find module './config/app'
 Require stack:
 - /app/index.js
     at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
     at Function.Module._load (node:internal/modules/cjs/loader:778:27)
     at Module.require (node:internal/modules/cjs/loader:1005:19)
     at require (node:internal/modules/cjs/helpers:102:18)
     at Object.<anonymous> (/app/index.js:8:34)
     at Module._compile (node:internal/modules/cjs/loader:1103:14)
     at Object.Module._extensions..js (node:internal/modules/cjs/loader:1157:10)
     at Module.load (node:internal/modules/cjs/loader:981:32)
     at Function.Module._load (node:internal/modules/cjs/loader:822:12)
     at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:77:12) {
   code: 'MODULE_NOT_FOUND',
   requireStack: [ '/app/index.js' ]
 }

and i really don't know why, because it works perfectly fine in my pc

the code for the whole project is actually much bigger, but only this files are the ones throwing me errors

Hope someone can help see what is happening that throws that error