An example of hand-written coroutines

The example we’ll use going forward is a simplified version of Rust’s asynchronous model. We’ll create and implement the following:

• Our own simplified Future trait
• A simple HTTP client that can only make GET requests
• A task we can pause and resume implemented as a state machine
• Our own simplified async/await syntax called coroutine/wait
• A homemade preprocessor to transform our coroutine/wait functions into state machines the same way async/await is transformed

So, to actually demystify coroutines, futures, and async/await, we will have to make some compromises. If we didn’t, we’d end up re-implementing everything that is async/await and futures in Rust today, which is too much for just understanding the underlying techniques and concepts.

Therefore, our example will do the following:

• Avoid error handling. If anything fails, we panic.
• Be specific and not generic. Creating...