$ git clone https://github.com/tom-wong168/knowledge-system.git
Cloning into 'knowledge-system'...
fatal: unable to connect to github.com:
github.com[0: 140.82.113.3]: errno=Unknown error
2,改https为git,git clone git://…
$ git clone git://github.com/tom-wong168/knowledge-system.git
Cloning into 'knowledge-system'...
fatal: unable to access 'https://github.com/tom-wong168/knowledge-system.git/': Failed to connect to github.com port 443 after 21069 ms: Couldn't connect to server
$ git clone git://github.com/tom-wong168/knowledge-system.git
Cloning into 'knowledge-system'...
fatal: unable to access 'https://github.com/tom-wong168/knowledge-system.git/': Failed to connect to github.com port 443 after 21071 ms: Couldn't connect to server