[bheadmaster]

> Questions like "What happens if I store `yield` somewhere and call it long after the loop ended?" and "What happens if I call `yield` from another thread during the loop?" naturally arise.

The fact that you can store `yield` somewhere allows for more flexible design of iterator functions, e.g. (written in a hurry as a proof of concept so will panic at the end): https://go.dev/play/p/QpVYmmC6g5b?v=gotip

Those hairy details may be hard to remember (or even decide), but they won't matter for most of the users - most users will just use `yield` in the simplest way, without storing them or calling them from another goroutine.