https://blog.wongcw.com/2018/12/26/ruby-2-6-0-%e6%ad%a3%e5%bc%8f%e7%99%bc%e5%b8%83%ef%bc%8c%e6%80%a7%e8%83%bd%e6%8f%90%e9%ab%981-7-%e5%80%8d/