Gracefully shutdown child process running with Overmind

Hi guys,

I have a couple of RQ workers running in a child process managed by overmind.
So my profile looks like this

web: uvicorn main:app --host --port 8080
chunk: python app/
transcript: python app/

and I have this in my docker file obviously.
CMD overmind start

Now when we shut down to restart, it seems the server only tries to shut down main process, which is causing issues cus I have ghost workers now.
How can I supply a script to run when we shutting things down?
Is there a way to define those processes in fly.toml? and also to pass through a script to shut them down?
If this is achievable with [processes] in fly.toml, how can I do that?