Magento 2

Magento FAQ: How To Generate a new SSH Key in Magento 2.0

Here's the article to connect to GitHub with SSH
https://help.github.com/articles/connecting-to-github-with-ssh/

please check for any existing ssh keys by running this command
ls -al ~/.ssh

If there are no keys setup, you need to follow these steps to generate a new SSH key and add it to the agent
https://help.github.com/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent/