Reminder that Rust does not automatically schedule anything. Unless you _explicitly_ call `tokio::spawn` or `async_std::spawn` you are still living entirely in state-machine land.

Rust's `join_all` uses `FuturesUnordered` behind the scenes, which is pretty intelligent in terms of keeping track of which tasks are ready to make progress, but it does not use tokio/async_std for scheduling. AFAICT the only thing being measured about tokio/async_std is the heap size of their `sleep` implementations.

I'd be very interesting in seeing how Tokio's actual scheduler performs. The two ways to do that are:

- using https://docs.rs/tokio/latest/tokio/task/join_set/struct.Join... to spawn all the futures and then await them

- spawn each future in the global scheduler, and then await the JoinHandles using the for loop from the appendix

As other commenters have noted, calling `sleep` only constructs a state machine. So the Appendix isn't actually concurrent. Again, you need to either put those state machines into the tokio/async_std schedulers with `spawn`, or combine the state machines with `FuturesUnordered`.