Describe how to setup sitemap generation with default_url_options Idea from: http://stackoverflow.com/questions/16720514/how-to-use-url-helpers-in-lib-modules-and-set-host-for-multiple-environments

routing.rb

#lib/routing.rb

# SO: http://stackoverflow.com/questions/16720514/how-to-use-url-helpers-in-lib-modules-and-set-host-for-multiple-environments
module Routing
  extend ActiveSupport::Concern
  include Rails.application.routes.url_helpers

  included do
    def default_url_options
      { :locale => I18n.locale }
    end
  end
end

sitemap.rb

# config/sitemap.rb

require Rails.root.join('lib/routing.rb')

### Logic of generating the sitemap
SitemapGenerator::Interpreter.send :include, Routing