连接不上github，也ping不通github

实测可用网址

http://tool.chinaz.com/dns?type=1&host=github.com&ip=

解决方案

https://blog.csdn.net/Hodors/article/details/105586996

https://www.cnblogs.com/mmit/p/12587287.html

https://zhuanlan.zhihu.com/p/162980381