Rushed Migration

Hack approach (not necessarily recommended, but has its uses):

• Add async in front of fns:

  pub fn t07_retrieve_information(..)
  pub async fn t07_retrieve_information(..)
  

• Change synchronous logic to asynchronous logic:

  std::thread::sleep(Duration::from_millis(delay));
  tokio::time::delay_for(Duration::from_millis(delay)).await
  

• Use types with asynchronous support:

  // synchronous -- will idly wait when there are no messages.
  let (tx, rx) = crossbeam::channel::unbounded::<_>();
  
  // asynchronous -- will switch to a different task when there are no messages.
  let (tx, rx) = tokio::sync::mpsc::unbounded_channel::<_>();
  

• Swap understandable errors for impossible ones (tokio#1835):

      error[E0308]: mismatched types
    --> src/main.rs:12:9
     |
  12 |         tokio::spawn(async move {
     |         ^^^^^^^^^^^^ one type is more general than the other
     |
     = note: expected type `std::ops::FnOnce<(std::iter::Map<_> + std::marker::Send>>,)>`
                found type `std::ops::FnOnce<(std::iter::Map<_> + std::marker::Send>>,)>`
  
  error: aborting due to previous error
  

And I show you a still more excellent way.