+if [[ $proxy ]]; then
+ a2enmod proxy proxy_http
+ # fyi: trailing slash is important
+ # reference: https://httpd.apache.org/docs/2.4/howto/reverse_proxy.html
+ cat >>$vhost_file <<EOF
+ ProxyPass "/" "http://$proxy/"
+ ProxyPassReverse "/" "http://$proxy/"
+EOF
+fi
+