Function map_ordered_concurrent 

pub async fn map_ordered_concurrent<I, T, F, Fut>(
    items: &[I],
    concurrency: usize,
    task: F,
) -> Vec<T>
where
    I: Clone + Send,
    T: Send,
    F: Fn(I) -> Fut + Send + Sync + 'static,
    Fut: Future<Output = T> + Send,