1.修改hosts文件：C:\Windows\System32\drivers\etc

# Github
151.101.44.249 github.global.ssl.fastly.net 
192.30.253.113 github.com 
103.245.222.133 assets-cdn.github.com 
23.235.47.133 assets-cdn.github.com 
203.208.39.104 assets-cdn.github.com 
204.232.175.78 documentcloud.github.com 
204.232.175.94 gist.github.com 
107.21.116.220 help.github.com 
207.97.227.252 nodeload.github.com 
199.27.76.130 raw.github.com 
107.22.3.110 status.github.com 
204.232.175.78 training.github.com 
207.97.227.243 www.github.com 
185.31.16.184 github.global.ssl.fastly.net 
185.31.18.133 avatars0.githubusercontent.com 
185.31.19.133 avatars1.githubusercontent.com
192.30.253.120 codeload.github.com

2.用管理员账号打开cmd，ipconfig /flushdns刷新DNS