channels in rust

weather.rs

let (tx, rx) = mpsc::channel();
for city in cities {
    let tx = tx.clone();
    let city = city.clone();
    thread::spawn(move || {
      let report = api_call(&city, &api_key);
      tx.send(report).unwrap();
    });
}
let mut reports : Vec<ApiResult> = Vec::with_capacity(cities.len());
for _ in cities {
  let rep = rx.recv().unwrap();
  reports.push(rep);
}