title: Use GitLab env variable in terraform file
body: <p>I have a secret stored as an env variable in GitLab : <code>TF_VAR_DD_API_KEY</code></p>
  <p>In my <code>main.tf</code> I am doing something like this:</p>
  <pre><code>{
    &quot;name&quot;: &quot;datadog-agent&quot;,
    &quot;image&quot;: &quot;datadog/agent:latest&quot;,
    &quot;environment&quot;: [
      {
        &quot;name&quot;: &quot;DD_API_KEY&quot;,
        &quot;value&quot;: &quot;${var.DD_API_KEY}&quot;
      }
    ]
  }
  </code></pre>
  <p>This doesn't seem to work. How can I get the value from the GitLab <code>TF_DD_API_KEY</code> variable and use it in my <code>main.tf</code> ?</p>
  <p>Thank you</p>