add support for gzipped HTTP/3 requests

http3/gzip_reader.go

@@ -0,0 +1,39 @@
+package http3
+
+// copied from net/transport.go
+
+// gzipReader wraps a response body so it can lazily
+// call gzip.NewReader on the first call to Read
+import (
+	"compress/gzip"
+	"io"
+)
+
+// call gzip.NewReader on the first call to Read
+type gzipReader struct {
+	body io.ReadCloser // underlying Response.Body
+	zr   *gzip.Reader  // lazily-initialized gzip reader
+	zerr error         // sticky error
+}
+
+func newGzipReader(body io.ReadCloser) io.ReadCloser {
+	return &gzipReader{body: body}
+}
+
+func (gz *gzipReader) Read(p []byte) (n int, err error) {
+	if gz.zerr != nil {
+		return 0, gz.zerr
+	}
+	if gz.zr == nil {
+		gz.zr, err = gzip.NewReader(gz.body)
+		if err != nil {
+			gz.zerr = err
+			return 0, err
+		}
+	}
+	return gz.zr.Read(p)
+}
+
+func (gz *gzipReader) Close() error {
+	return gz.body.Close()
+}