Problem of testing SSH in git behind proxy

Error
like: 'ssh: github.com: no address associated with name'

solve:

setting http.proxy will not work for ssh. You need to proxy your ssh connection. See this description.
To summarize:

Start git-cmd.bat and create ~/.ssh/config (

notepad
%home%\.ssh\config.

)

ProxyCommand /bin/connect.exe -H proxy.server.name:3128 %h %p

Host github.com
User git
Port 22
Hostname github.com
IdentityFile "C:\users\username\.ssh\id_rsa"
TCPKeepAlive yes
IdentitiesOnly yes

Host ssh.github.com
User git
Port 443
Hostname ssh.github.com
IdentityFile "C:\users\username\.ssh\id_rsa"
TCPKeepAlive yes
IdentitiesOnly yes

(set the correct proxy hostname:port, and the path to id_rsa. When you use git-bash, use slashes in the path to id_rsa)

Now 

ssh
github.com

 should work