Like here's David's "Build Your Own Async" [1], which I prefer over Philip's (still extremely good) "What the heck is the event loop anyway?" [2].
It's one thing to tell how something works, but to successfully show what the hell its actually doing under the covers, just conveys much more information.
A similar snippet[1] exists for go, and it doesn't do anything particularly special either.
I don't know, maybe David beazley has altered my sense of what "from scratch" means.
[1] https://gist.github.com/lizrice/a5ef4d175fd0cd3491c7e8d71682...