https://blog.wongcw.com/2018/12/05/%e5%bd%b1%e9%a6%b3%e7%99%bc%e5%b8%83%e5%85%a8%e6%96%b0t%e7%b3%bb%e5%88%97%e7%a7%bb%e5%8b%95%e7%a1%ac%e7%9b%a4%ef%bc%9atype-c%e6%8e%a5%e5%8f%a3%e6%89%8b%e6%a9%9f%e7%9b%b4%e9%80%a3/