Netcat (nc / ncat) cannot be interrupted in Docker - docker

Question

I have a service that does some tasks and then opens a port so that other services know it's finished. I use nc to do that: nc -l -k -p 1337. I use docker-compose to manage services.
When shutting down the services, the service running nc always takes several seconds to close while it should be instant. I think the process doesn't interrupt and docker has to kill it. If I run nc on the same service via docker-compose run I cannot interrupt the process via Ctrl+C.
When running nc locally it can instantly be terminated via Ctrl+C.
How can I create a service running nc -l -k -p 1337 which can be interrupted?
Dockerfile
FROM ruby:2.6.3-alpine
RUN apk add --no-cache netcat-openbsd
COPY entrypoint.sh ./
RUN chmod +x entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
entrypoint.sh
#!/bin/sh
# ...
nc -l -k -p 1337
docker-compose.yml
services:
nc:
build:
context: .
dockerfile: Dockerfile
docker-compose up --build
OR:
entrypoint.sh
#!/bin/sh
# ...
exec "$#"
docker-compose.yml
services:
nc:
build:
context: .
dockerfile: Dockerfile
command: nc -l -k -p 1337
docker-compose up --build
docker-compose run --rm nc nc -l -k -p 1337

Answer 1

Assuming nc actually responds to signals under normal circumstances, you need to:
Use exec
Use the list version of command.
So in the first case, add an exec to the shell script.
And in the second case, probably need command: ["nc", "-l", "-k", "-p", "1337"] in the compose file.
See https://hynek.me/articles/docker-signals/ for full checklist.