code: func (s *ChangesService) AddReviewer(changeID string, input *ReviewerInput) (*AddReviewerResult, *Response, error) {
  	u := fmt.Sprintf("changes/%s/reviewers", changeID)
  
  	req, err := s.client.NewRequest("POST", u, input)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	v := new(AddReviewerResult)
  	resp, err := s.client.Do(req, v)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return v, resp, err
  }
docs: // AddReviewer adds one user or all members of one group as reviewer to the change.
  // The reviewer to be added to the change must be provided in the request body as a ReviewerInput entity.
  //
  // As response an AddReviewerResult entity is returned that describes the newly added reviewers.
  // If a group is specified, adding the group members as reviewers is an atomic operation.
  // This means if an error is returned, none of the members are added as reviewer.
  // If a group with many members is added as reviewer a confirmation may be required.
  //
  // Gerrit API docs: https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#add-reviewer