Dockerfile

FROM python:3.9
WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
ENTRYPOINT ["python", "-m", "gunicorn", "--bind", ":8080", "--workers", "1", "--threads", "8", "--timeout", "0", "main:app"]

main.py

import os

from flask import Flask, request

app = Flask(__name__)

@app.route('/')
def index():
    return ("$HOME is %s." % os.environ.get("HOME"), 200)

if __name__ == "__main__":
    app.run(debug=False, host='0.0.0.0', port=int(os.environ.get('PORT', 8080)))

requirements.txt

Flask
gunicorn