安装下载certbot
https://certbot.eff.org/instructions?ws=nginx&os=ubuntuxenial
执行
certbot run -a manual -i nginx -d *.zhongwutao.xyz
dns配置TXT记录
确定公网解析，大概1分钟
回车，继续
生成证书
/etc/letsencrypt/live/zhongwutao.xyz-0001/fullchain.pem ssl_certificate
/etc/letsencrypt/live/zhongwutao.xyz-0001/privkey.pem ssl_certificate_key
