Fix Bug: retry scrape will lost POST requestData

[Shinku-Chen]

when retry scrape
requestData will loss in http.NewRequest

so Seek requestData before scrape.NewRequest

req.ContentLength  always 0 and

if req.GetBody != nil && req.ContentLength == 0 {
			req.Body = NoBody
			req.GetBody = func() (io.ReadCloser, error) { return NoBody, nil }
		}

[Shinku-Chen]

@WGH-

[WGH-]

I don't think it's a good idea to limit the API to seekable bodies.

However, we might try to rewind the body if it happens to implement io.Seeker. And it might be a good idea to make Retry retry an error if doesn't.

[Shinku-Chen]

是个好主意
现在已经按照需求修改了代码
请帮忙检查一下 感谢

That's a great idea.
The code has now been modified according to the requirements.
Please help me check it out, thank you.

[WGH-]

Otherwise, looks good

[WGH-]

And thank you!