Auto generate a ssh key in Checkout SSH keys on Circleci

If you needs to generate a new ssh key for checkout you repository from Github to circleci to build tests, do:

1. Login on Circleci and access the project settings.
2. Enter in the "Permissions" > "Checkout SSH keys".
3. Remove all ssh keys that you have. A new session called "Add user key" will be presented, then click on the button in this session called "Create and Add <user name> user key". In this moment the circleci create a new ssh key, save the private key and add the public key on your account on github.