In Rust, calling an async function from a sync function looks like this[0]: block_on(myasyncfn()) This basically repeatedly polls the future returned by t

In Rust, calling an async function from a sync function looks like this[0]: block_on(myasyncfn()) This basically repeatedly polls the future returned by the async function, until it completes, and then returns it. (you can also call a full-featured executor like Tokio, but for simple stuff block_on is perfect) My mental model is like this: just like you use await to wait for a future in an async context, you use block_on to wait for a future in a sync context. You only need to call block_on on the top-level future, meaning that myasyncfn() can have a lot of futures underneath. The only thing that won't work is spawning other tasks (new top-level futures that can continue executing even after the future returned by the function completes). Which is actually amazing: after block_on returns, there is no async background tasks lurking on: the program just continues as a normal non-async program. I don't know how async is in other languages, but I guess that every language has something equivalent to block_on? How on Earth you integrate async code into sync code otherwise? As an aside, calling a potentially blocking sync function from an async function is easy too, like this[1]: spawn_blocking(myblockingsyncfn) This spawns a new OS thread (or reuse one from the threadpool dedicated to blocking operations), then run the provided function in there. spawn_blocking returns a future that, when awaited, waits for the function in the other thread to complete, and then returns its value. [0] https://docs.rs/futures/0.3.17/futures/executor/fn.block_on.html https://docs.rs/futures/0.3.17/futures/executor/fn.block_on.... [1] here the exact function to call depends on the executor you use to run the event loop of your async program, but all major ones provides a spawn_blocking API, like https://docs.rs/tokio/1.12.0/tokio/task/fn.spawn_blocking.html https://docs.rs/tokio/1.12.0/tokio/task/fn.spawn_blocking.ht... and https://docs.rs/async-std/1.10.0/async_std/task/fn.spawn_blocking.html https://docs.rs/async-std/1.10.0/async_std/task/fn.spawn_blo...