code: func (s *MarketplaceService) ListPlans(ctx context.Context, opt *ListOptions) ([]*MarketplacePlan, *Response, error) {
  	uri := s.marketplaceURI("plans")
  	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 plans []*MarketplacePlan
  	resp, err := s.client.Do(ctx, req, &plans)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return plans, resp, nil
  }
docs: // ListPlans lists all plans for your Marketplace listing.
  //
  // GitHub API docs: https://developer.github.com/v3/apps/marketplace/#list-all-plans-for-your-marketplace-listing