Add the following content to the hosts file of the system
192.30.253.112 github.com
185.199.108.153 assets-cdn.github.com
185.199.109.153 assets-cdn.github.com
185.199.110.153 assets-cdn.github.com
185.199.111.153 assets-cdn.github.com
199.232.5.194 github.global.ssl.fastly.net
Just make hosts effective