add http hijack methods (#555)

rest/handler/authhandler.go

@@ -1,8 +1,10 @@
 package handler
 
 import (
+	"bufio"
 	"context"
 	"errors"
+	"net"
 	"net/http"
 	"net/http/httputil"
 
@@ -138,6 +140,12 @@ func (grw *guardedResponseWriter) Header() http.Header {
 	return grw.writer.Header()
 }
 
+// Hijack implements the http.Hijacker interface.
+// This expands the Response to fulfill http.Hijacker if the underlying http.ResponseWriter supports it.
+func (grw *guardedResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return grw.writer.(http.Hijacker).Hijack()
+}
+
 func (grw *guardedResponseWriter) Write(body []byte) (int, error) {
 	return grw.writer.Write(body)
 }