encoding: Implement http.Hijacker in gzipWriter through delegation

encoding/gzip.go

@@ -9,8 +9,11 @@ Package encoding contains Content-Encoding related filters.
 package encoding
 
 import (
+	"bufio"
 	"compress/gzip"
+	"errors"
 	"io"
+	"net"
 	"net/http"
 	"strings"
 	"sync"
@@ -58,6 +61,13 @@ func (w *gzipWriter) WriteHeader(code int) {
 	w.ResponseWriter.WriteHeader(code)
 }
 
+func (w *gzipWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if hj, ok := w.ResponseWriter.(http.Hijacker); ok {
+		return hj.Hijack()
+	}
+	return nil, nil, errors.New("not a Hijacker")
+}
+
 func (w *gzipWriter) init() error {
 	w.Lock()
 	defer w.Unlock()

encoding/gzip_test.go

@@ -153,3 +153,20 @@ func TestGzipper_WriteHeader(t *testing.T) {
 		}
 	}
 }
+
+func TestGzipper_Hijacker(t *testing.T) {
+	srv := httptest.NewServer(Gzipper(gzip.DefaultCompression)(
+		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if _, ok := w.(http.Hijacker); !ok {
+				t.Error("underlying http.ResponseWriter should implement http.Hijacker")
+			}
+		}),
+	))
+	defer srv.Close()
+
+	resp, err := http.Get(srv.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+}