Workling/Starling: killing a background work from a controller


There is something I don't understand with Workling/Starling: it is
easy to start a background work from a controller, but is it possible
to stop this background work from a controller?

Say for example:
user input -> controller triggers background work aaa
another user input -> controller kills background work aaa

I know that when you call MyWorker.asynch_my_method it returns a UID,
but I don't understand how to use it to kill it?

Thanks a lot!