add_subscriber

# File actioncable/lib/action_cable/subscription_adapter/subscriber_map.rb, line 11
      def add_subscriber(channel, subscriber, on_success)
        @sync.synchronize do
          new_channel = [email protected]?(channel)

          @subscribers[channel] << subscriber

          if new_channel
            add_channel channel, on_success
          elsif on_success
            on_success.call
          end
        end
      end