title: Github Actions and git clone issue
body: <p>Having some problems using git clone from within a Github Actions, i get the following no matter what i try:</p>
  
  <p>The code that fails in my main.yml:</p>
  
  <pre><code>jobs:
   terraform:
     name: 'Terraform with Github Actions!'
     runs-on: ubuntu-latest
     steps:
     - name: 'Login to Azure'
      uses: azure/login@v1
      with:
        creds: ${{ secrets.AZURE_CREDENTIALS }}
    - name: 'Checkout'
      uses: actions/checkout@master
    - name: 'Preparing blueprint-environment'
      run: |
        snip
        git clone git@github.com:ourcompany/whateverrepo.git
  </code></pre>
  
  <p>Error message:</p>
  
  <p>git@github.com: Permission denied (publickey).</p>
  
  <p>Ive seen many posts on adding ssh-keys, but thats locally, not in a ubuntu-release running from Github actions - what am i missing here? I cant generate ssh-keys and add the private key on the fly to the Github repo-settings, how can i fix this?</p>