This design seems very similar to async in scala except that in scala the execution context is an implicit parameter rather than an explicit parameter. I did not find this api to be significantly better for many use cases than writing threads and communicating over a concurrent queue. There were significant downsides as well because the program behavior was highly dependent on the execution context. It led to spooky action at a distance problems where unrelated tasks could interfere with each and management of the execution context was a pain. My sense though is that the zig team has little experience with scala and thus do not realize the extent to which this is not a novel approach, nor is it a panacea.