Bug fix:

 - fatal error: concurrent map writes(gin-contrib#15)

timeout.go

@@ -85,9 +85,11 @@ func New(opts ...Option) gin.HandlerFunc {
 			tw.FreeBuffer()
 			bufPool.Put(buffer)
 
-			c.Writer = w
-			t.response(c)
-			c.Writer = tw
+			// Copy gin.Context here to avoid concurrent writes to c.ResponseWriter's header(which is a map),
+			// see https://github.com/gin-contrib/timeout/issues/15
+			ctxCopy := c.Copy()
+			ctxCopy.Writer = w
+			t.response(ctxCopy)
 		}
 	}
 }

timeout_test.go

@@ -100,3 +100,26 @@ func TestPanic(t *testing.T) {
 	assert.Equal(t, http.StatusInternalServerError, w.Code)
 	assert.Equal(t, "", w.Body.String())
 }
+
+func TestConcurrentHeaderWrites(t *testing.T) {
+	r := gin.New()
+	r.Use(gin.Recovery())
+	r.Use(New(
+		WithTimeout(time.Millisecond*50),
+		WithHandler(func(c *gin.Context) {
+			c.Next()
+		}),
+	))
+	r.GET("/", func(c *gin.Context) {
+		for {
+			c.Header("X-Foo", "bar")
+		}
+	})
+
+	w := httptest.NewRecorder()
+	req, err := http.NewRequest(http.MethodGet, "/", nil)
+	if err != nil {
+		t.Fatal("http NewRequest: ", err)
+	}
+	r.ServeHTTP(w, req)
+}