add hijacker

main.go

@@ -1,11 +1,56 @@
 package traefik_response_header_forward_plugin
 
 import (
+	"bufio"
+	"bytes"
 	"context"
 	"fmt"
+	"io"
+	"net"
 	"net/http"
 )
 
+var (
+	_ interface {
+		http.ResponseWriter
+		http.Hijacker
+	} = &wrappedResponseWriter{}
+)
+
+type wrappedResponseWriter struct {
+	rw   http.ResponseWriter
+	buf  *bytes.Buffer
+	code int
+}
+
+func (w *wrappedResponseWriter) Header() http.Header {
+	return w.rw.Header()
+}
+
+func (w *wrappedResponseWriter) Write(b []byte) (int, error) {
+	return w.buf.Write(b)
+}
+
+func (w *wrappedResponseWriter) WriteHeader(code int) {
+	w.code = code
+}
+
+func (w *wrappedResponseWriter) Flush() {
+	w.rw.WriteHeader(w.code)
+	io.Copy(w.rw, w.buf)
+}
+
+func (w *wrappedResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hijacker, ok := w.rw.(http.Hijacker)
+	if !ok {
+		return nil, nil, fmt.Errorf("%T is not an http.Hijacker", w.rw)
+	}
+
+	return hijacker.Hijack()
+}
+
+// ========================================
+
 type RequestHeader struct {
 	Name string `json:"name,omitempty"`
 }
@@ -23,7 +68,7 @@ func CreateConfig() *Config {
 type ResponseHeaderForward struct {
 	next   http.Handler
 	name   string
-	requestHeaders []RequestHeader
+	config *Config
 }
 
 func New(ctx context.Context, next http.Handler, config *Config, name string) (http.Handler, error) {
@@ -40,19 +85,26 @@ func New(ctx context.Context, next http.Handler, config *Config, name string) (h
 	return &ResponseHeaderForward{
 		next:   next,
 		name:   name,
-		requestHeaders: config.RequestHeaders,
+		config: config,
 	}, nil
 }
 
 func (a *ResponseHeaderForward) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
-	a.next.ServeHTTP(rw, req)
+	resp := &wrappedResponseWriter{
+		rw:  rw,
+		buf: &bytes.Buffer{},
+	}
 
-	// for _, requestHeader := range a.requestHeaders {
-	// 	headerValue := req.Header.Get(requestHeader.Name)
-	// 	if headerValue == "" {
-	// 		continue
-	// 	}
+	defer resp.Flush()
 
-	// 	rw.Header().Set(requestHeader.Name, headerValue)
-	// }
+	a.next.ServeHTTP(resp, req)
+
+	for _, requestHeader := range a.config.RequestHeaders {
+		headerValue := req.Header.Get(requestHeader.Name)
+		if headerValue == "" {
+			continue
+		}
+
+		resp.Header().Set(requestHeader.Name, headerValue)
+	}
 }