Move content encoding in the beginning of the middleware chain, update dependencies

http/middleware/compress/gogzip.go

@@ -0,0 +1,55 @@
+package compress
+
+import (
+	"compress/gzip"
+	"io"
+	"sync"
+)
+
+type gogzipImpl struct {
+	pool sync.Pool
+}
+
+func NewGoGzip(level Level) Compression {
+	gzipLevel := gzip.DefaultCompression
+	if level == BestCompression {
+		gzipLevel = gzip.BestCompression
+	} else if level == BestSpeed {
+		gzipLevel = gzip.BestSpeed
+	}
+
+	g := &gogzipImpl{
+		pool: sync.Pool{
+			New: func() interface{} {
+				w, err := gzip.NewWriterLevel(io.Discard, gzipLevel)
+				if err != nil {
+					return nil
+				}
+				return w
+			},
+		},
+	}
+
+	return g
+}
+
+func (g *gogzipImpl) Acquire() Compressor {
+	c := g.pool.Get()
+	if c == nil {
+		return nil
+	}
+
+	x, ok := c.(Compressor)
+	if !ok {
+		return nil
+	}
+
+	x.Reset(io.Discard)
+
+	return x
+}
+
+func (g *gogzipImpl) Release(c Compressor) {
+	c.Reset(io.Discard)
+	g.pool.Put(c)
+}