Async Callback about analytics-go

[achille-roussel]

@f2prateek what's your take on that?

[f2prateek]

IIRC we've done this language dependendent. On Android/iOS we always do the callback on the main thread, but for Java we leave it undefined. It's the application's responsibility to make sure the callback doesn't block.

[achille-roussel]

OK, it seems like not over-engineering this is good, we can still revisit and loosen the requirements later if that's something users will find interesting.

I'll add documentation to make it explicit that there are no guarantees on which goroutine calls the callbacks and they shouldn't make long blocking operations.

Thanks!

[f2prateek]

SGTM!