pardon the question as I am new to backend deployment
I have the a very simple program

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder

app = FastAPI()

@app.get('/')
async def root():
    return jsonable_encoder({'message': 'hello world'})

I deploy on Heroku with the Procfile as so

web: uvicorn main:app --workers 4

I’m getting the following error

Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of launch

I have read some other questions such as
/questions/14322989/first-heroku-deploy-failed-error-code-h10

They ask to make sure that I’m listening on the right port, the one that Heroku provides. However I’m not specifying any port in the code so I’m not sure how I can fix this?