wireguard-tools/contrib/reresolve-dns
..
README
reresolve-dns.sh

reresolve-dns
=============

Run this script from cron every thirty seconds or so, and it will ensure
that if, when using a dynamic DNS service, the DNS entry for a hosts
changes, the kernel will get the update to the DNS entry.

This works by parsing configuration files, and simply running:
    $ wg set wg0 peer ... endpoint ...