Count file lines fast in Go

utils.go

func LineCounter(r io.Reader) (int, error) {
    buf := make([]byte, 32*1024)
    count := 0
    lineSep := []byte{'\n'}

    for {
        c, err := r.Read(buf)
        count += bytes.Count(buf[:c], lineSep)

        switch {
        case err == io.EOF:
            return count, nil

        case err != nil:
            return count, err
        }
    }
}