app.set error when deploying node app on docker

I have developed an API using express js that works fine. I use VS code and start the app by doing "node app.js" in terminal. I now want to deploy this api on a server using docker. I have followed this guide: https://github.com/nodejs/docker-node/blob/main/README.md#how-to-use-this-image and I am using the docker-compose option. The docker-compose.yml:

version: "2"
services:
  node:
    image: "node:current-alpine3.12"
    user: "node"
    working_dir: /home/node/app
    environment:
      - NODE_ENV=production
    volumes:
      - ./node:/home/node/app
    expose:
      - "80"
    command: "npm start"

I have copied all files from my VS code project using scp to the ./node folder mentioned in the docker file. I then get this error when running docker-compose up:

TypeError: app.set is not a function


    at Object.<anonymous> (/home/node/app/bin/www:16:5)


    at Module._compile (node:internal/modules/cjs/loader:1097:14)


    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1149:10)


    at Module.load (node:internal/modules/cjs/loader:975:32)


    at Function.Module._load (node:internal/modules/cjs/loader:822:12)


    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)


    at node:internal/main/run_main_module:17:47



Node.js v17.2.0


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In my app.js I do not use app.set. I read about someone else having issues when setting port. I use app.listen(80, () => console.log("Listening on port 80")); to set the correct port. I am not sure why I get an app.set error. How do I fix this issue?