Error: can’t chdir to ‘app’ when using docker start container [closed]

#!/bin/sh

gunicorn app:app -w 2 --threads 2 -b 0.0.0.0:80

# OR

gunicorn --chdir /app app:app -w 2 --threads 2 -b 0.0.0.0:80

# OR

gunicorn --chdir . app:app -w 2 --threads 2 -b 0.0.0.0:80