An actor is a reference type that protects access to its mutable state, and is introduced with the keyword `actor`.
Global actors make it possible to safely work with global variables in a concurrent program, as well as modeling other global program constraints.
A simple way, similar to a `let` binding, to create child tasks and await their results using `async let` declarations.
Everything you need to build elegant asynchronous apps after concurrency features introduced in Swift 5.5 like async/await, Tasks, and Actors.