Function snocat::util::finally_async

pub async fn finally_async<T, E, FT: Future<Output = Result<T, E>>, FC: Future<Output = Result<(), E>>>(
    cb: impl FnOnce() -> FT, 
    cleanup: impl FnOnce(&mut Result<T, E>) -> FC
) -> Result<T, E>

Run a block, then, regardless of success/failure, run another block, with access to the results. Exceptions from the first block are preferred, then from the finally block, then successes