Checksum file

func ChecksumFile(fn string) string {
    file, err := os.Open(fn)

    if err != nil {
        panic(err.Error())
    }

    defer file.Close()

    info, _ := file.Stat()

    filesize := info.Size()

    blocks := uint64(math.Ceil(float64(filesize) / float64(filechunk)))

    hash := md5.New()

    for i := uint64(0); i < blocks; i++ {
        blocksize := int(math.Min(filechunk, float64(filesize-int64(i*filechunk))))
        buf := make([] byte, blocksize)

        file.Read(buf)
        io.WriteString(hash, string(buf))
    }

    return fmt.Sprintf("%x", hash.Sum(nil))

}