You might have already implemented TLS (using one of the ways mentioned in the example of security section), and have setup your server to listen to port 443 (for HTTPS).
Also see [`redirect_to_https`](https://docs.rs/actix-web-lab/0/actix_web_lab/middleware/fn.redirect_to_https.html) from [`actix-web-lab`](https://crates.io/crates/actix-web-lab).