Refreshing an SSL certificate in Express

I'm using a letsencrypt certificate on an Express server to enable https. The certificate is automatically renewed by a cron job running certbot-auto periodically.

Express reads the certificate file at startup. Do I need to do something to let Express know when the certificate is renewed, or will it pick up the changes automatically? If I need to manually refresh it, how would I do so without restarting the whole app?