Problem deploying only Apollo Server to heroku - express

Question

I am deploying an Apollo Server for my database to heroku and it is giving an application error. It is not simply show that there is a problem with the get route, it says that the application has an error and the error logs say that the app is crashing. It runs fine locally.
I have set up the procfile with: web: node app.js .
I have tried it with the procfile removed.
I have set playground and introspection to true. I saw that that could be the problem but it did not seem to help.
The port is set to process.env.PORT || 8080 .
Here is the minimal code:
const { ApolloServer } = require('apollo-server-express');
const express = require('express');
const db = require('./models');
const typeDefs = require('./data/schema');
const resolvers = require('./data/resolvers');
const app = express();
const server = new ApolloServer({
typeDefs,
resolvers,
context: { db },
introspection: true,
playground: true,
});
server.applyMiddleware({ app });
const PORT = process.env.PORT || 8080;
app.get('/', (req, res) => {
res.send('hello');
});
app.listen(PORT, () => {
console.log(`Server is ready at ${PORT}`);
});
I am also using some other functions (trying to set up a cron process), but those are commented out.
I would expect to get the / get route to at least say hello, or for the /graphql route to display playground. I am getting neither of those options.

Answer 1

It turns out that I needed to add the following to package.json:
"scripts": {
"start": "app.js",
...
}
And I needed to install packages listed in the heroku logs --tail, but I have had those errors before. Writing the script start key into the package.json file is for when you are deploying your server independently of your react (or client) side.