Configuring an nginx reverse proxy

Put this into something like /etc/nginx/sites-enabled/yoursite and test the config with sudo nginx -t. If everything passed reload nginx with sudo systemctl reload nginx.

server {

    listen 443;

    index index.html index.htm index.nginx-debian.html;

    server_name example.com;

    location / {
        client_max_body_size 200M;
        proxy_set_header Host $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_pass http://localhost:3000;
    }

    include /etc/letsencrypt/options-ssl-nginx.conf;
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;


    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
}

server {
    if ($host = $host) {
        return 301 https://$host$request_uri;
    }
    server_name $host;
    return 404;
}