Yet another dockerized mkcert (though it's been done before).

Generate a certificate:

docker run -it --rm \
  --volume "${PWD}:/.local/share/mkcert" \
  flesch/mkcert "*.example.com"

docker run -it --rm \
  --volume "${PWD}:/.local/share/mkcert" \
  flesch/mkcert -key-file "example-key.pem" \
  -cert-file "example.pem" "*.example.com"

As mkcert runs inside a container, the local CA won't be installed on the host machine. mkcert -install will only create rootCA.pem — you will need to install it manually.

On macOS, you can manually install rootCA.pem like so:

sudo security add-trusted-cert -d -r trustRoot \
  -k /Library/Keychains/System.keychain ${PWD}/rootCA.pem