I am trying to deploy my Flask app (to https://railway.app/).

My project structure looks like this:

myproject/server
├── Procfile
├── __init__.py
├── app.py
├── requirements.txt
├── sources
│   ├── __init__.py
│   ├── integrations
│   ├── source_controller.py
│   ├── sources.py

And in app.py, I have the following imports:

from flask import Flask, request

from server.sources.source_controller import SourceController
from server.sources.sources import Source

While I can run my server just fine locally (with flask --app app run), when I try calling gunicorn app:app (which is what railway calls when deploying my app), I get the following error:

[2024-07-02 19:43:34 -0400] [65259] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/gunicorn/arbiter.py", line 609, in spawn_worker
    worker.init_process()
  File "/usr/local/lib/python3.11/site-packages/gunicorn/workers/base.py", line 134, in init_process
    self.load_wsgi()
  File "/usr/local/lib/python3.11/site-packages/gunicorn/workers/base.py", line 146, in load_wsgi
    self.wsgi = self.app.wsgi()
                ^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
                    ^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/gunicorn/app/wsgiapp.py", line 58, in load
    return self.load_wsgiapp()
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/gunicorn/app/wsgiapp.py", line 48, in load_wsgiapp
    return util.import_app(self.app_uri)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/gunicorn/util.py", line 371, in import_app
    mod = importlib.import_module(module)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/Cellar/[email protected]/3.11.6_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1204, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1176, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1147, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 690, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 940, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/Users/marcoeangeli/Projects/tomes/server/app.py", line 3, in <module>
    from server.sources.source_controller import SourceController
ModuleNotFoundError: No module named 'server'
[2024-07-02 19:43:34 -0400] [65259] [INFO] Worker exiting (pid: 65259)
... other logs ...

I have tried searching for this error but I can’t find anything that helps. I pretty confused why my IDE is happy with the way I’m importing, running the app directly runs fine, but Gunicorn fails!