I am learning Rust and I am writing a unit test using mockall library.
I have some String in my test and I want to pass it to multiple mock closures.

If I pass it directly, then I understand that I would move the ownership to the closure.
So instead I am converting it to &str, but then I get “borrowed value does not live long enough” and “argument requires that is borrowed for `’static”.

I can’t uderstand why the compiler can’t figure out that the String lives long enough as &str in this case. I can make it work using Rc, but I would like to know if there is easier way to fix this.

Here is the mockall return_once signature

use mockall::mock;

pub struct Setting {
    pub key: String,
}

impl Clone for Setting {
    fn clone(&self) -> Self {
        Setting {
            key: self.key.clone(),
        }
    }
}

pub trait TSettingRepository {
    fn get(&self, id: &str) -> Setting;
}

mock! {
    pub SettingRepository{}

    impl TSettingRepository for SettingRepository {
        fn get(&self, id: &str) -> Setting {
            todo!()
        }
    }
}

fn main() {
    let key_str: String = "some String from external function".to_string();
    let key: &str = &key_str; //<- borrowed value does not live long enough

    let mut setting_repository = MockSettingRepository::new();

    setting_repository.expect_get().return_once(|_| Setting {
        key: key.to_string(),
    });

    setting_repository.expect_get().return_once(|_| Setting {
        key: key.to_string(),
    });
}