title: SSH connect to github fail
body: <p>I typed the command to have a connection test to <code>github</code>:</p>
  
  <pre><code>ssh -T git@github.com
  </code></pre>
  
  <p>but it outputs:</p>
  
  <pre><code>ssh: Could not resolve hostname github.com: nodename nor servname provided, or not known
  </code></pre>
  
  <p>why ssh could not resolve github.com? I want to know this and how to solve it?</p>