You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: config.rs
    path of file: ./repos/rust-jwt-hs256/src
    
    the code of the file until where you have to start completion: #[derive(Debug, Clone)]
pub struct Config {
    pub database_url: String,
    pub jwt_secret: String,
    pub jwt_expires_in: String,
    pub jwt_maxage: i32,
}

impl Config {
    pub fn init() -> Config {
        let database_url = std::env::var("DATABASE_URL").expect("DATABASE_URL must be set");
        let jwt_secret = std::env::var("JWT_SECRET").expect("JWT_SECRET must be set");
        let jwt_expires_in 
    
    pub fn init() -> Config {
        let database_url = std::env::var("DATABASE_URL").expect("DATABASE_URL must be set");
        let jwt_secret = std::env::var("JWT_SECRET").expect("JWT_SECRET must be set");
        let jwt_expires_in = std::env::var("JWT_EXPIRED_IN").expect("JWT_EXPIRED_IN must be set");
        let jwt_maxage = std::env::var("JWT_MAXAGE").expect("JWT_MAXAGE must be set");
        Config {
            database_url,
            jwt_secret,
            jwt_expires_in,
            jwt_maxage: jwt_maxage.parse::<i32>().unwrap(),
        }
    }