make write calls in a single go thread

[kucukaslan]

In current implementation, each thread calls write after it read 32 MB block data concurrently. So I guess this causes the same problem by issuing multiple concurrent write request.
https://github.com/Kucukaslan/PoCSequentiality/blob/5a52a241093c09140d326294196f72cff672cd90/main.go#L131

It would be better if each thread can send data to a writer thread via a channel and that thread sequentially issue the write requests.

channel can receive a struct like

struct {
    data        *[]byte
    startIndex    int
    length        int
}

[kucukaslan]

It might be better to write another program for it, just in case it actually works.
s3qet is in my mind as a name BTW. Combining "s3", "s3q"uential writes, and get (as "qet").