I think I'm getting the picture from this and other replies. To get close to a sense of structured concurrency I've had to lean on a plugin that handles worker threads (or would have to write one myself), and tie this in with async/await language features, and add some checks to handle thread lifetime and error states.

It would be really nice to have a first class language feature to wrap all this up, it sounds like that's what structured concurrency as a concept is aiming towards.