Simplified FileSize function

utils.go

@@ -163,13 +163,7 @@ func HashFile(filename string) (hash string, err error) {
 
 // FileSize returns the size of a file
 func FileSize(filename string) (int, error) {
-	f, err := os.Open(filename)
-	if err != nil {
-		return -1, err
-	}
-	defer f.Close()
-
-	fi, err := f.Stat()
+	fi, err := os.Stat(filename)
 	if err != nil {
 		return -1, err
 	}

utils_test.go

@@ -26,8 +26,8 @@ func TestFileSize(t *testing.T) {
 		if err == nil {
 			t.Error("should return an error")
 		}
-		if s > 0 {
-			t.Errorf("size should be 0, got: %d", s)
+		if s != -1 {
+			t.Errorf("size should be -1, got: %d", s)
 		}
 	})
 }