It should be at `Start()` cause it's a property of each task, right? If you set it with `SetOptions()` it's for the full process list group, so either all tasks are cancel-able or none is.

I'm especially interested in the documentation feedback, cause I think I have thoroughly explained the precise behavior. I'd really like to know if that's not clear enough. In particular, here's the section talking about panics vs. routines and cleanup:

>Finally, please note that cancellation requests yield panics in the same routine that called Start() with that given identifier. However, it's not unusual for servers to spawn additional Go routines to handle the same request. The application is responsible of cleaning up, if there are additional resources that should be recycled. The proper way to do this is...