fix id parsing

chord/id.go

@@ -57,6 +57,6 @@ func ParseID(s string) (ID, error) {
 		return ID{}, errors.New("invalid ID")
 	}
 	var id ID
-	_, err := hex.AppendDecode(id[:], []byte(s))
+	_, err := hex.AppendDecode(id[:0], []byte(s))
 	return id, err
 }