From b5118f65a202f7625ee5d5fdc376f59c5cc8a872 Mon Sep 17 00:00:00 2001
From: keitosuwahara <keitosuwahara0816@gmail.com>
Date: Sun, 13 Jul 2025 22:57:28 +0900
Subject: [PATCH] Prevention of Hijack() runtime panics

---
 response_writer.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/response_writer.go b/response_writer.go
index 753a0b09..ab2f5fec 100644
--- a/response_writer.go
+++ b/response_writer.go
@@ -6,6 +6,7 @@ package gin
 
 import (
 	"bufio"
+	"errors"
 	"io"
 	"net"
 	"net/http"
@@ -16,6 +17,8 @@ const (
 	defaultStatus = http.StatusOK
 )
 
+var errHijackAlreadyWritten = errors.New("gin: response already written")
+
 // ResponseWriter ...
 type ResponseWriter interface {
 	http.ResponseWriter
@@ -106,6 +109,9 @@ func (w *responseWriter) Written() bool {
 
 // Hijack implements the http.Hijacker interface.
 func (w *responseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if w.Written() {
+		return nil, nil, errHijackAlreadyWritten
+	}
 	if w.size < 0 {
 		w.size = 0
 	}