app.values_of("modules")
            .unwrap()
            .map(|x| x.clone())
            .cloned()
            .collect()

error[E0277]: the trait bound `str: std::clone::Clone` is not satisfied
  --> src/main.rs:49:14
   |
49 |             .cloned()
   |              ^^^^^^ the trait `std::clone::Clone` is not implemented for `str`