Function for_each 

pub fn for_each<I, F, T>(i: I, f: F)
where
    I: Iterator<Item = T>,
    F: Fn(T) + Sync,
    T: Send,

Calls the closure on each element of the iterator in parallel, waiting for all closures to finish.

• The closure does not require 'static lifetime since the for_each function bounds the lifetime of all submitted closures.
• The closure must be Sync as multiple threads will refer to it.
• The iterator items must be Send as they will be sent from one thread to another.