Async exercises

[mo8it]

The book will got a new chapter about async. We should add some async exercises.

[Polycarbohydrate]

Any update on this? I would like to see some async exercises as well. :)

[mo8it]

Now that the async chapter is added to the book, I am open to exercise ideas :)

[Polycarbohydrate]

Sound good 👍! I'll probably start thinking of ideas and start on async1.

I think we should probably put the async exercise folder after 20_threads (because of the ordering of the book and it just makes sense to do async exercises after learning concurrency) and async would be #21, 21_async. Would need to shift the rest of the exercises' respective numbers as well.

For the exercises, I was thinking at the very least, there would be 4 exercises to cover the lengthy chapter as well as most of the key points covered. In the book, the example code shown uses trpl for many async methods but I feel like using tokio would work better as it is well-known and used. Like the rest of the rustlings exercises, this section should start with some simple concepts of asynchronous programming in Rust and then work toward more advanced features (if wanted).

[mo8it]

Tokio for sure. Rustlings v6 allows adding dependencies to exercises, but this possibility is not used in any exercise yet.

[Polycarbohydrate]

Rustlings v6 allows adding dependencies to exercises

Is there any documentation for this? I tried looking in the changelog and version history but I can't find anything.

[mo8it]

You just add the dependency to the dev/Cargo.toml file.

[Polycarbohydrate]

Created a PR: #2216

Fails the dev check (which I explained in the comment below the PR) and the MacOS check. Feedback is welcome :)