[$] Zig explores structured concurrency

Version 0.16.0 of the Zig programming language was recently announced, and with it an expanded version of the new Io interface that we covered in December. The new interface is based on an idea called structured concurrency that makes writing correct concurrent applications easier. Zig's implementation of the idea is more explicit and verbose than other languages, however, which could offer an opportunity to explore the consequences of different designs.