> You can't tell by the function call itelf. You can't know that in general. Any regular Go function could spawn a goroutine return immediately too. In JS a "b

> You can't tell by the function call itelf. You can't know that in general. Any regular Go function could spawn a goroutine return immediately too. In JS a "blocking" function could call setImmediate(…) and return too. Even in C, a function could spawn a thread and return immediately too. You never know at the call site whether a function will block or not, in any language. So I think polled futures actually are closest to knowing this, since the block-or-not decision can be bubbled up to the caller. In Rust the "doesn't block" example would more likely be `runtime.spawn(foo())`, since the executor is not built into the language, so spawning asynchronously is easier when left up to the caller.