March 13, 2018, Let’s Encrypt Wildcard certificate support is live.
How to use it? Follow me.
git clone https://github.com/certbot/certbot.git
./certbot-auto certonly --manual -d *.example.com --agree-tos --manual-public-ip-logging-ok --preferred-challenges dns-01 --server https://acme-v02.api.letsencrypt.org/directory