code: func (s *RepositoriesService) ListCollaborators(ctx context.Context, owner, repo string, opt *ListCollaboratorsOptions) ([]*User, *Response, error) {
  	u := fmt.Sprintf("repos/%v/%v/collaborators", owner, repo)
  	u, err := addOptions(u, opt)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	req.Header.Set("Accept", mediaTypeNestedTeamsPreview)
  
  	var users []*User
  	resp, err := s.client.Do(ctx, req, &users)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return users, resp, nil
  }
docs: // ListCollaborators lists the GitHub users that have access to the repository.
  //
  // GitHub API docs: https://developer.github.com/v3/repos/collaborators/#list-collaborators