Function join_all_concurrent 

pub async fn join_all_concurrent<T, R, F>(items: Vec<T>, f: F) -> Vec<R>
where
    T: Send + 'static,
    R: Send + 'static,
    F: Fn(T) -> BoxFuture<R> + Send + Clone + 'static,

Simple concurrent batch that spawns all tasks at once Returns results in input order