fix golint issues in core/stores (#527)

core/stores/redis/scriptcache.go

@@ -12,13 +12,16 @@ var (
 )
 
 type (
+	// Map is an alias of map[string]string.
 	Map map[string]string
 
+	// A ScriptCache is a cache that stores a script with its sha key.
 	ScriptCache struct {
 		atomic.Value
 	}
 )
 
+// GetScriptCache returns a ScriptCache.
 func GetScriptCache() *ScriptCache {
 	once.Do(func() {
 		instance = &ScriptCache{}
@@ -28,12 +31,14 @@ func GetScriptCache() *ScriptCache {
 	return instance
 }
 
+// GetSha returns the sha string of given script.
 func (sc *ScriptCache) GetSha(script string) (string, bool) {
 	cache := sc.Load().(Map)
 	ret, ok := cache[script]
 	return ret, ok
 }
 
+// SetSha sets script with sha into the ScriptCache.
 func (sc *ScriptCache) SetSha(script, sha string) {
 	lock.Lock()
 	defer lock.Unlock()