Add a way to cancel actions

[mostafa]

From act/registry.go:253:

// TODO: Add a way to cancel the action.

This can be achieved using context.WithTimeout or something similar, just like policy evaluation timeout.

[Hamsajj]

Hello, I'd like to work on this if no one else is.

Do you want to add a timeout option to async actions and their config? or create a way to signal them somehow to be canceled?

[mostafa]

Hey @Hamsajj,

I want both sync and async functions to have a timeout, so that they can be cancelled either via a timeout or calling the cancel function. In the future, maybe we can have a list of running actions, especially long-running async ones, so we can cancel them via the API or the #472. The scope of this ticket is to only have the timeout cancellation.