Some comments:

Async/await syntax is poorly documented across the ecosystem but has landed now and is useful, without it codebases will look outdated soon enough, hyper itself has some of the best docs

Lazystatic is popular way to use globals like that yet don't really bother with it anymore. The paradigms are a bit different for a language, you are discouraged from such things for a reason, there's certainly ways around using globals.

You don't need extern crate with 2018 edition and macros are automatically imported