git clone 出现fatal: unable to access ‘https://github.com/xxx: Failed to connect to github.com

问题描述：
使用git clone命令时，出现如下错误：
fatal: unable to access ‘https://github.com/xxx’: Failed to connect to github.com port 443: Timed out

解决方案：
将"https"改为"git"即可，如： ‘git://github.com/xxx’