subscribe_to_internal_channel

# File actioncable/lib/action_cable/connection/internal_channel.rb, line 16
        def subscribe_to_internal_channel
          if connection_identifier.present?
            callback = -> (message) { process_internal_message decode(message) }
            @_internal_subscriptions ||= []
            @_internal_subscriptions << [ internal_channel, callback ]

            server.event_loop.post { pubsub.subscribe(internal_channel, callback) }
            logger.info "Registered connection (#{connection_identifier})"
          end
        end