unfortunately they've never really taken off so folks reach for explicit state machines instead. there have been a handful of options on the jvm over the years (e.g. quasar, kilim) but they're all abandoned now, the loom continuation API is internal with no hint of it becoming public, kotlin's aren't serializable and the issue is inactive (
https://github.com/Kotlin/kotlinx.coroutines/issues/76), etc.. such a shame