Error [ERR_STREAM_WRITE_AFTER_END]: write after end ExpressJS - node.js

Question

I forked a repo I found and running it locally was fine with no errors however I wanted to run it locally on https so I changed the code of src/index.js
const server = createServer();
to
const options = {
key: fs.readFileSync('localhost-key.pem'),
cert: fs.readFileSync('localhost.pem')
};
const server = https.createServer(options, app)
But I started getting the error after the change when I try to access the website on https://localhost:8080
Full Error:
node:events:491
throw er; // Unhandled 'error' event
^
Error [ERR_STREAM_WRITE_AFTER_END]: write after end
at new NodeError (node:internal/errors:399:5)
at write_ (node:_http_outgoing:868:11)
at ServerResponse.write (node:_http_outgoing:827:15)
at ReadStream.ondata (node:internal/streams/readable:766:22)
at ReadStream.emit (node:events:513:28)
at addChunk (node:internal/streams/readable:324:12)
at readableAddChunk (node:internal/streams/readable:297:9)
at Readable.push (node:internal/streams/readable:234:10)
at node:internal/fs/streams:275:14
at FSReqCallback.wrapper [as oncomplete] (node:fs:681:5)
Emitted 'error' event on ServerResponse instance at:
at ServerResponse.onerror (node:internal/streams/readable:785:14)
at ServerResponse.emit (node:events:525:35)
at emitErrorNt (node:_http_outgoing:846:9)
at process.processTicksAndRejections (node:internal/process/task_queues:83:21) {
code: 'ERR_STREAM_WRITE_AFTER_END'
}