Password Validation

Write a simple program checking user inputs against a secret string.

The main logic checking user input is simple:

    if password == PASSWORD {
        println!("Welcome!");
    } else {
        println!("I don't know you.");
    }

It is a common practice to not show the user's password when reading it. To do so, we can use the crate rpassword:

    let password = rpassword::read_password().expect("Failed to read the password.");