This doesn't make sense in Go. Nothing is asynchronous in Go, everything is blocking. You use goroutines to execute multiple tasks at the same time. That's a big part of what makes Go simple: it's a lot easier to understand sequential code than spaghetti callbacks and promises (it's somewhat similar to async/await in the JavaScript world).
Go’s unsophisticated type system makes it difficult to write a good standard generic data structure library such as a future/promise library.
That leads to people either writing a poor replacement, not using that style, or losing type safety. This is precisely what you would predict upon learning golang doesn’t have user defined genetics & ive had it bite me more than once in real projects.
I think people are used to futures etc, that's why the new concept feels strange.
I think the goroutines and channels are the biggest features which compensates for generics.