code: func (t *TLSRenewer) SetExpectedRole(role string) {
  	t.mu.Lock()
  	t.expectedRole = role
  	t.mu.Unlock()
  }
docs: // SetExpectedRole sets the expected role. If a renewal is forced, and the role
  // doesn't match this expectation, renewal will be retried with exponential
  // backoff until it does match.