Nginx rewrite path to point back to root

gistfile1.txt

        # This will rewrite 1.2.3.4/sub back to 1.2.3.4:3000
        location /sub {
                rewrite /sub(.*) $1 break;
                proxy_set_header   X-Real-IP $remote_addr;
                proxy_set_header   Host      $http_host;
                proxy_pass         http://localhost:3000;
        }