nginx-config

In /etc/nginx/sites-enabled

file: sub.domain.com:

server {
        server_name sub.domain.com;

        location / {
                proxy_pass http://localhost:PORT;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection "upgrade";
                proxy_read_timeout 86400;
        }
}

Then generate certificate with certbot