fix:sig

@@ -67,7 +67,7 @@ class Signature
         $this->sortByASCII();
 
         $string = $this->map($this->item, function ($k, $v) {
-                return !($v === '' || $v === null);
+                return !($v === '' || $v === null || $k === 'service');
             }) . '&key=' . $secret;
 
         return self::encode($string);