fix golint issues in core/stores (#527)

core/stores/cache/config.go

@@ -3,8 +3,10 @@ package cache
 import "github.com/tal-tech/go-zero/core/stores/redis"
 
 type (
+	// A ClusterConf is the config of a redis cluster that used as cache.
 	ClusterConf []NodeConf
 
+	// A NodeConf is the config of a redis node that used as cache.
 	NodeConf struct {
 		redis.RedisConf
 		Weight int `json:",default=100"`