title: is there a way to use your current credentials to assume a service account instead of having to use the json key?
body: <p>My personal account is an admin in my gcp project.</p>
  
  <p>If I want to use one of the service accounts I have created (from my local laptop) I do this:</p>
  
  <pre><code>gcloud auth activate-service-account --key-file=some-service-account.json
  </code></pre>
  
  <p>But I wonder, if I already have my own admin account active, is there a way to just assume a service account without the key? Can GCP use my current creds to give me access to assume that service account? </p>
  
  <p>If so this also makes me wonder if I can use service accounts applied to GCE instances the same way. So I can attach a service account to a GCE instance that gives it access to assume <em>other</em> service accounts.</p>