dns解析慢，github上不去，慢
修改host.
windows下路径为：C:\Windows\System32\drivers\etc\hosts
Linux下路径：/etc/hosts
加入：
192.30.253.112 github.com 192.30.253.119 gist.github.com 151.101.100.133 assets-cdn.github.com 151.101.100.133 raw.githubusercontent.com 151.101.100.133 gist.githubusercontent.com 151.101.100.133 cloud.githubusercontent.com 151.101.100.133 camo.githubusercontent.com 151.101.100.133 avatars0.githubusercontent.com 151.101.100.133 avatars1.githubusercontent.com 151.101.100.133 avatars2.githubusercontent.com 151.101.100.133 avatars3.githubusercontent.com 151.101.100.133 avatars4.githubusercontent.com 151.101.100.133 avatars5.githubusercontent.com 151.101.100.133 avatars6.githubusercontent.com 151.101.100.133 avatars7.githubusercontent.com 151.101.100.133 avatars8.githubusercontent.com