Actually, D suports "fibers" where you have a "Task". Then you can switch the task handler to another implementation and have Go-like M:N coroutines. The default handlers in the stdlib are only thread based or single-thread coroutines but Vibe.d for example supports Go-like coroutines.

Still, Go is really hard to beat on that front because it makes it super easy and has the really brilliant feature of making almost everything that waits for IO interruptable inside a function when you call "go function()" without having to mark operations with "async".