1) Whenever it's done 2) let me know and possibly ...

# exposed

[shredder121]

1) Whenever it's done 2) let me know and possibly 3) continue more work (so 'it', the unit of work and 'me', the calling context must be kept for later use).
You could for example close over them.
I am however not an expert, so if anyone has a better analogy? But I do see the pain points.
Basically, in non reactive programming you can just let the error bubble up the call stack, but that doesn't work in reactive programming.