fn get_or<'a>(key: &'a String, default_value: &'a String) -> &'a String {
    if key.starts_with("i am key") {
        key
    } else {
        default_value
    }
}

fn main() {
    let key = String::from("not a key");
    let result = get_or(&key, &String::from("default value"));
    dbg!(result);
}