From 559aefeb85bf38c1947494f71e1b9f8f8531400c Mon Sep 17 00:00:00 2001
From: wjqserver <114663932+WJQSERVER@users.noreply.github.com>
Date: Sun, 29 Mar 2026 16:05:09 +0800
Subject: [PATCH] fix(SSE): capture Writer before goroutine, use select for
 channel send

Address PR review feedback:
- Capture w := c.Writer before goroutine start, use w (not c.Writer)
  inside the goroutine to avoid holding *Context reference
- Move channel send into select alongside context cancellation in all
  examples and tests, preventing goroutine leak when client disconnects
  while blocked on unbuffered send
---
 docs/sse.md | 14 +++++++-------
 sse.go      | 16 ++++++++--------
 sse_test.go |  3 +--
 3 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/docs/sse.md b/docs/sse.md
index b0224e8..1b44521 100644
--- a/docs/sse.md
+++ b/docs/sse.md
@@ -45,6 +45,7 @@ r.GET("/events", func(c *touka.Context) {
 ```go
 r.GET("/events-chan", func(c *touka.Context) {
     eventChan := make(chan touka.Event)
+    ctx := c.Request.Context()
 
     // 在独立的 goroutine 中发送事件.
     go func() {
@@ -52,14 +53,13 @@ r.GET("/events-chan", func(c *touka.Context) {
 
         for i := 0; i < 10; i++ {
             select {
-            case <-c.Request.Context().Done():
+            case <-ctx.Done():
                 return // 客户端已断开, 退出 goroutine.
-            default:
-                eventChan <- touka.Event{
-                    Data: fmt.Sprintf("消息 #%d", i),
-                }
-                time.Sleep(1 * time.Second)
+            case eventChan <- touka.Event{
+                Data: fmt.Sprintf("消息 #%d", i),
+            }:
             }
+            time.Sleep(1 * time.Second)
         }
     }()
 
@@ -70,7 +70,7 @@ r.GET("/events-chan", func(c *touka.Context) {
 
 ## 最佳实践
 
-1. **资源回收**: `EventStreamChan` 是阻塞的，handler 在事件流结束前不会返回。请确保生产者 goroutine 在 `select` 中监听 `c.Request.Context().Done()` 以响应客户端断开。
+1. **资源回收**: `EventStreamChan` 是阻塞的，handler 在事件流结束前不会返回。将 `c.Request.Context().Done()` 和 `eventChan <- ...` 作为同一个 `select` 的两个分支，确保发送操作本身能够响应客户端断开。
 2. **关闭 Channel**: 生产者完成发送后必须 `close(eventChan)`，否则 handler 会永远阻塞。
 3. **数据格式**: SSE 协议要求数据为 UTF-8。Touka 的 `Render` 方法会自动处理多行数据并加上必要的 `data:` 前缀。
 4. **超时管理**: SSE 连接通常是长连接，请确保您的反向代理（如 Nginx）配置了足够大的写超时时间。
diff --git a/sse.go b/sse.go
index 3ce050a..0284775 100644
--- a/sse.go
+++ b/sse.go
@@ -132,13 +132,12 @@ func (c *Context) EventStream(streamer func(w io.Writer) bool) {
 //	            select {
 //	            case <-c.Request.Context().Done():
 //	                return // 客户端已断开, 退出 goroutine.
-//	            default:
-//	                eventChan <- touka.Event{
-//	                    Id:   fmt.Sprintf("%d", i),
-//	                    Data: "hello from channel",
-//	                }
-//	                time.Sleep(2 * time.Second)
+//	            case eventChan <- touka.Event{
+//	                Id:   fmt.Sprintf("%d", i),
+//	                Data: "hello from channel",
+//	            }:
 //	            }
+//	            time.Sleep(2 * time.Second)
 //	        }
 //	    }()
 //
@@ -155,7 +154,8 @@ func (c *Context) EventStreamChan(eventChan <-chan Event) {
 	c.Writer.Flush()
 
 	// 捕获稳定的引用, 不持有 *Context 指针, 以免 Context 被 pool 回收后出现竞态.
-	fl, _ := c.Writer.(http.Flusher)
+	w := c.Writer
+	fl, _ := w.(http.Flusher)
 	reqCtx := c.Request.Context()
 
 	goroutineExited := make(chan struct{})
@@ -170,7 +170,7 @@ func (c *Context) EventStreamChan(eventChan <-chan Event) {
 				if !ok {
 					return
 				}
-				if err := event.Render(c.Writer); err != nil {
+				if err := event.Render(w); err != nil {
 					return
 				}
 				if fl != nil {
diff --git a/sse_test.go b/sse_test.go
index f50859a..cfb9ae3 100644
--- a/sse_test.go
+++ b/sse_test.go
@@ -68,8 +68,7 @@ func TestEventStreamChanUnblocksOnClientDisconnect(t *testing.T) {
 			select {
 			case <-ctx.Done():
 				return
-			default:
-				eventChan <- Event{Data: "tick"}
+			case eventChan <- Event{Data: "tick"}:
 				time.Sleep(10 * time.Millisecond)
 			}
 		}