主要是參考「Configuring DNS-over-TLS on macOS」這篇的方法做的：
brew install knot-resolver
echo "policy.add(policy.all(policy.TLS_FORWARD({{'1.1.1.1', hostname='1.1.1.1'}})))" | tee -a /usr/local/etc/kresd/config
sudo brew services restart knot-resolver
然後 127.0.0.1 就有 DNS resolver 可以用了，接下來就是把系統的 DNS 改過去...