code: func (w *SegmentWAL) Reader() WALReader {
  	return &repairingWALReader{
  		wal: w,
  		r:   newWALReader(w.files, w.logger),
  	}
  }
docs: // Reader returns a new reader over the the write ahead log data.
  // It must be completely consumed before writing to the WAL.