I don’t agree with your comment about Map and ForEach, just by virtue of the fact that sync.Map exists in Go’s standard library.

But your point about the lack of contexts is definitely a deal breaker for me personally too.

The "map" under discussion here is very different from sync.Map. The discussion here is focused on the "map" primitive from functional programming - transforming a collection by applying a function to each element.

sync.Map is a concurrency-safe hash map. Same name, totally different thing.