Simple NGINX example
server {
    listen 80;
    listen 443 ssl;
    server_name example.com;

    # Set the lets encrypt certificate
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    # Set the lets encrypt private key
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

    location / {
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_redirect off;

        proxy_pass http://$IP:$PORT;
    }
}