Merge branch 'emqx' into v2

pkg/protocol/topic.go

@@ -2,7 +2,6 @@ package protocol
 
 import (
 	"errors"
-	"fmt"
 	"strings"
 )
 
@@ -112,7 +111,6 @@ func parseLast(topics []string) (topicInfo *TopicInfo, err error) {
 
 func GetCommandTopic(deviceCode, productKey string) string {
 	topic := strings.Join([]string{TopicHeadThing, "down", "command", productKey, deviceCode}, "/")
-	fmt.Printf("topic:%s\r\n", topic)
 	return topic
 }