When using a docker to run gitlab-runner Unregister runners at container stop

Description

I use https://hub.docker.com/r/gitlab/gitlab-runner to run a gitlab runner, I can register a runner then run it, but when the container is killed all runners are left registered in Gitlab.

Moreover I'd like to kill all launched docker-machine before exiting.

Proposal

I think some options to automatically unregister the runners and kill launched docker-machine would do.