https://blog.wongcw.com/2018/11/07/net-standard-2-1%e7%99%bc%e5%b8%83%ef%bc%9a%e9%80%b2%e4%b8%80%e6%ad%a5%e4%bd%bf-net%e5%af%a6%e7%8f%be%e4%b8%80%e8%87%b4/