some problem about gzip writer not use sync pool in middleware/compress.go

[imxyb]

Looking at the git commit history, I found that the sync pool of the gzip writer was removed. The reason is to fix the issue here: labstack/armor#13. But I still don't understand the reason for this deletion. I guess tha Is it because there is no way to return an error when using sync pool?

the removed code:

func gzipPool(config GzipConfig) sync.Pool {
	return sync.Pool{
		New: func() interface{} {
                        // can not return error here
			w, _ := gzip.NewWriterLevel(ioutil.Discard, config.Level)
			return w
		},
	}
}

[pafuent]

I did the change and I could see some improvements on the speed and the number of allocations. Please take a look at the PR and check that the implementation makes sense.