Support early termination (e.g. break)

[carstenbauer]

E.g. break within @tasks as mentioned in #95 (comment)

[adienes]

maybe break should be required to be guarded behind @one_by_one (or just @break )

[disberd]

I started using OhMyThreads and I have to say I like it a lot so far, but indeed I use this for speeding up long running simulations and I'd like to be able to interrupt the execution (while also interrupting the execution of the various tasks spawned by @tasks to avoid hogging CPU for an interrupted simulation till the end of the original @tasks iteration).

At the moment i resort to throwing an error within the body of @tasks for stopping early like so:

mutable struct AbortController
    @atomic stop::Bool
end
AbortController() = AbortController(false)

controller = AbortController()
try
	@tasks for i in 1:100
		if @atomic(controller.stop)
			error("Aborted")
		end
		sleep(2) # expensive computation
		@info i
	end
finally
	@atomic controller.stop = true
end

which seems to correctly kill the spawned tasks.

Is there a better way to achieve this?

@carstenbauer, @MasonProtter