Should await yield same result each time ? Why not just use existing Promise library like this ?

[MarcWeber]

If you come from JS world you expect await to await a promise.
Thus awaiting multiple times should yield the same result.
A mature promise library seems to be this. There are more on github:

https://eryn.io/roblox-lua-promise/docs/WhyUsePromises

const wrap = (f) => (...args) => new Promise((r,j) => f(args, (e,r) => { if (err) j(err); r(r) }))

And that wrapper already exists from changelog:

• Promise.promisify now uses coroutine.wrap instead of `Promise.spawn

but that requires tasks and some game engine..

Here is yet another implementation:
https://github.com/javalikescript/luajls