perf: lessen wasting time for pubsub (#229)

Author: supercaracal

lib/redis_client/cluster/pub_sub.rb

@@ -22,7 +22,7 @@ def close
 
         def take_message(timeout)
           @worker = subscribe(@client, timeout) if @worker.nil?
-          return if @worker.join(0.01).nil?
+          return if @worker.alive?
 
           message = @worker[:reply]
           @worker = nil