code: func InvalidateExecution(c context.Context, auth *dm.Execution_Auth) (a *Attempt, e *Execution, err error) {
  	if a, e, err = verifyExecutionAndCheckExTok(c, auth); err != nil {
  		logging.Fields{ek: err, "eid": auth.Id}.Errorf(c, "failed to verify execution")
  		err = makeError(err, "requires execution Auth")
  		return
  	}
  
  	err = e.Revoke(c)
  	if err != nil {
  		logging.Fields{ek: err, "eid": auth.Id}.Errorf(c, "failed to revoke execution")
  		err = makeError(err, "unable to invalidate Auth")
  	}
  	return
  }
docs: // InvalidateExecution verifies that the execution key is valid, and then
  // revokes the execution key.
  //
  // As a bonus, it will return the loaded Attempt and Execution.