[Nullabillity]

async/await is just syntactic sugar for futures/promises. The future API itself generally lends itself towards structured concurrency, but your particular implementation may not be.

For example, Rust's `Future` is structured (although executors may introduce escape hatches), while JavaScript's `Promise` is unstructured.

[didibus]

Can you explain a little how Rust adds cancellation and retry supervision using future? I'm not familiar with Rust.