fix golint issues in core/stores (#527)

core/stores/redis/redisblockingnode.go

@@ -7,11 +7,13 @@ import (
 	"github.com/tal-tech/go-zero/core/logx"
 )
 
+// ClosableNode interface represents a closable redis node.
 type ClosableNode interface {
 	RedisNode
 	Close()
 }
 
+// CreateBlockingNode returns a ClosableNode.
 func CreateBlockingNode(r *Redis) (ClosableNode, error) {
 	timeout := readWriteTimeout + blockingQueryTimeout