clone github仓库时老是提示22端口超时，如下：
$ git clone [email protected]:xtod/yuwang.git
Cloning into 'yuwang'...
ssh: connect to host github.com port 22: Connection timed out
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
还提示是否对该仓库具有访问权或者仓库是否存在，这不废话么，我肯定确认。
于是试着ssh -T了一下，看能不能访问，但提示的还是22端口超时
$ ssh -T [email protected]
ssh: connect to host github.com port 22: Connection timed out
现在来看应该是访问问题，在此把访问端口改为443吧，不用22了，编辑~/.ssh/config写入如下内容：
Host github.com
HostName ssh.github.com
User git
Port 443
PreferredAuthentications publickey
IdentityFile ~/.ssh/id_ed25519
然后再ssh -T试一下
$ ssh -T [email protected]
Hi xtod! You've successfully authenticated, but GitHub does not provide shell access.
好了，可以正常使用了。