There's an experimental feature in Go that lets you write python-like generators that work with range() and the callback is called `yield`. Here's some details: https://go.dev/wiki/RangefuncExperiment

That's probably what the post is talking about.

(I personally don't love this change, but now that it's clear Go 2.0 won't happen, it seems like some of the more outlandish ideas are making it into Go 1.x. Ah well.)