Function get_first_ok_bounded 

pub async fn get_first_ok_bounded<Iter, I, T, E, F, Fut>(
    items: Iter,
    concurrent: usize,
    checker: F,
) -> Option<Result<T, E>>
where
    F: FnOnce(I) -> Fut + Send + Copy + 'static,
    Fut: Future<Output = Result<T, E>> + Send,
    I: Send + 'static,
    T: Send + 'static,
    E: Send + 'static,
    Iter: ExactSizeIterator<Item = I> + Send + 'static,

Returns the first non-error result from a function checker applied to each entry in a list of items. If the list of items is empty, it returns None. If all of the results are errors, it returns the last error. There are concurrent workers to apply the checker function. If concurrent is 0, then it will create len(items) workers.