Use AsyncLocalStorage if available

[mcollina]

https://nodejs.org/dist/latest-v14.x/docs/api/async_hooks.html#async_hooks_class_asynclocalstorage provides a very similar experience of cls-hooked at a fraction of the overhead. It should use that instead when/if available.

[thorough-developer]

@mcollina Good call! I will look into implementing this asap!

[thorough-developer]

@mcollina Am I waiting on this PR: nodejs/node#32318 ? for a backport to 12?

[thorough-developer]

@mcollina Got this implemented. I see a 33% increase in performance on average which is pretty amazing. Just waiting on the backport: https://github.com/thorough-developer/fastify-http-context/tree/async-local-storage

[mcollina]

I know :). I was part of the team that came up with the theory that makes it possible to be faster.

[thorough-developer]

Done #6

Added a conditional to handle whether the class was available. So 13+ and hopefully 12 soon will get the performance boost. Thanks for the suggestion