carry lang param

app/controllers/application_controller.rb

@@ -99,6 +99,10 @@ class ApplicationController < ActionController::Base
     I18n.with_locale(locale, &)
   end
 
+  def lang
+    params[:lang].presence
+  end
+
   def with_browser_locale(&)
     return yield if I18n.locale != :'en-US' && I18n.locale != :en