fn read_config<P: AsRef<Path>>(config_file: P) -> Result<ServerConfig, Box<dyn Error>> {

    let content = std::fs::read_to_string(config_file)?;

    Ok(serde_json::from_str(&content)?)

}

async fn main() -> Result<(), Box<dyn Error>> {

    let mut args = std::env::args();

    args.next();

    let config_file = args

        .next()

        .unwrap_or_else(|| "server_config.json".to_string());

    let config = read_config(&config_file)

        .unwrap_or_else(|_| panic!("Could not read config {}.", config_file));

    let app = create_app(config)?;

    let listener = tokio::net::TcpListener::bind("0.0.0.0:8000").await.unwrap();

    axum::serve(listener, app)

        .with_graceful_shutdown(shutdown_signal())

        .await?;

    println!("shutting down");

    Ok(())

async fn shutdown_signal() {

    let ctrl_c = async {

        tokio::signal::ctrl_c()

    let terminate = async {

        tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate())

            .expect("failed to install signal handler")

            .recv()

            .await;

    };

    tokio::select! {

        _ = ctrl_c => {},

        _ = terminate => {},

    }

}