[developerDan]

This is just a hunch but likely because of the application the two languages were originally designed for. Go is/was a purely backend lang (as I understand it) whereas Swift was built with the UI in mind which must be run on the main thread. So Swift has async/await for making clear boundaries between synchronous (aka UI) operations and asynchronous operations.

I’m am not well educated on the subject though so take that with a grain of salt.

[kbolino]

This is a good point. It's possible to use Go this way too, but it gets tricky. You can lock the main goroutine to its O/S thread with runtime.LockOSThread and then do the heavy lifting on other goroutines, sending messages back to the main goroutine typically using channels. Given Swift's lineage, this is probably more ergonomic there than in Go.