Added Functionality to Point path to default Img

Sometimes the image is not found and for those artist/albums there is no
way for pointing the image path to default image path so some helper
functions have been added so that we can point them to default Image.

cache/cache.go

@@ -12,12 +12,17 @@ var (
 	USER_CACHE_DIR, err                      = os.UserCacheDir()
 	CACHE_LIST          map[[2]string]string = make(map[[2]string]string)
 	CACHE_DIR           string               = USER_CACHE_DIR
+	DEFAULT_IMG         string
 )
 
 func SetCacheDir(path string) {
 	CACHE_DIR = path
 }
 
+func SetDefaultPath(path string) {
+	DEFAULT_IMG = path
+}
+
 func LoadCache(path string) error {
 	cacheFileContent, err := ioutil.ReadFile(path)
 	if err != nil {
@@ -43,6 +48,10 @@ func GetFromCache(artist, album string) (string, error) {
 	}
 }
 
+func PointToDefault(artist, album string) {
+	CACHE_LIST[[2]string{artist, album}] = DEFAULT_IMG
+}
+
 func AddToCache(artist, album string) string {
 	fileName := CACHE_DIR + GenerateName(artist, album)
 	CACHE_LIST[[2]string{artist, album}] = fileName