FWIW I really don't like async in rust. It's improved significantly over the past couple years and it's nowhere near as bad as callback hell in Javascript but things still feel opaque. I've been toying around with a little monitoring agent (think Nagios or Sensu) to keep an eye on my defective LG fridge. So far I've managed to crash rustc twice. Trying to wrap my head around one library (that I was using incorrectly) I managed to "fork bomb" the damn thing and realize that I've little to no insight into the runtime. Try to find the current number of running tasks being managed by tokio…
The beauty of the rust async stuff is that you can move to a multi-threaded runtime as you desire with minimal effort.