FWIW, there's an effort to do exactly that, but because it will require language level changes and it is just on the drawing board phase, it will likely be a while before it can be widely used.
The "optionality" of `async` while sharing code also applies for `const` and mutability (why do we need `Deref` and `DerefMut`?). Finding a solution that can work for these three (and maybe others?) parts of the language will be a welcome improvement.
