code: func (s *MarketplaceService) ListPlanAccountsForPlan(ctx context.Context, planID int64, opt *ListOptions) ([]*MarketplacePlanAccount, *Response, error) {
  	uri := s.marketplaceURI(fmt.Sprintf("plans/%v/accounts", planID))
  	u, err := addOptions(uri, opt)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	var accounts []*MarketplacePlanAccount
  	resp, err := s.client.Do(ctx, req, &accounts)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return accounts, resp, nil
  }
docs: // ListPlanAccountsForPlan lists all GitHub accounts (user or organization) on a specific plan.
  //
  // GitHub API docs: https://developer.github.com/v3/apps/marketplace/#list-all-github-accounts-user-or-organization-on-a-specific-plan