just a fyi<p>//! What whorl isn't:
//! - Performant, this is an adaptation of a class I gave at Rustconf a few
//! years back. Its first and foremost goal is to teach <i>how</i> an executor
//! works, not the best way to make it fast. Reading the tokio source
//! code would be a really good thing if you want to learn about how to make
//! things performant and scalable.