This is usually false, in Rust and elsewhere. Futures are tasks that run on whatever thread is scheduling them. They are an even lighter-weight version of green threads/fibers/M:N.
But only if you await them in that thread. If you `spawn` them, they can be executed in another free thread; although you'll miss the return value in this case.
So for people new to async/await in rust, how a web server usually works:
Request/response future is spawned to the runtime, and a thread decides to take the future for execution if the runtime uses multithreading.
Inside of this request/response future whatever futures are .awaited will continue the execution in the same thread when ready.
Users can also spawn futures inside the request/response future, which might go to another thread. The result of this future is not available for the spawning thread.
Some executors have special functions, such as `blocking` that will execute the block in another thread, giving the result back to the awaiting thread when finished.
This is usually false, in Rust and elsewhere. Futures are tasks that run on whatever thread is scheduling them. They are an even lighter-weight version of green threads/fibers/M:N.