Feature request: use the security key the instance was launched with if it exists in ~/.ssh

[dginther]

Would it be possible to pull the key name when pulling the instance information, and check ~/.ssh for <key_name>.pem, and to add a -i ~/.ssh/<key_name>.pem onto the arguments list so that it would automatically use the right pem key?

I am not much of a Go programmer, or I'd submit a pull req.