clean up codes

wal.go

@@ -714,10 +714,7 @@ func (w *SegmentWAL) Close() error {
 		return errors.Wrapf(hf.Close(), "closing WAL head %s", hf.Name())
 	}
 
-	if w.dirFile != nil {
-		w.dirFile.Close()
-	}
-	return nil
+	return w.dirFile.Close()
 }
 
 const (

wal_test.go

@@ -273,7 +273,7 @@ func TestWALRestoreCorrupted_invalidSegment(t *testing.T) {
 	Ok(t, err)
 	f2, err := wal.createSegmentFile(dir + "/000002")
 	Ok(t, err)
-	Ok(t, f2.Close()) // close for windows!
+	Ok(t, f2.Close())
 
 	// Make header of second segment invalid.
 	_, err = f.WriteAt([]byte{1, 2, 3, 4}, 0)