From 6e320c97e83a61df3daa0f28695a736bece3104b Mon Sep 17 00:00:00 2001
From: Samuel Abreu <sdepaula@gmail.com>
Date: Mon, 27 May 2019 03:04:30 -0300
Subject: [PATCH] Fix context.Params race condition on Copy() (#1841)

* Fix context.Params race condition on Copy()

Using context.Param(key) on a context.Copy inside a goroutine
may lead to incorrect value on a high load, where another request
overwrite a Param

* Using waitgroup to wait asynchronous test case
---
 context.go      |  3 +++
 context_test.go | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/context.go b/context.go
index 425b627..3f1f8ca 100644
--- a/context.go
+++ b/context.go
@@ -89,6 +89,9 @@ func (c *Context) Copy() *Context {
 	for k, v := range c.Keys {
 		cp.Keys[k] = v
 	}
+	paramCopy := make([]Param, len(cp.Params))
+	copy(paramCopy, cp.Params)
+	cp.Params = paramCopy
 	return &cp
 }
 
diff --git a/context_test.go b/context_test.go
index e8dcd3d..89cfb44 100644
--- a/context_test.go
+++ b/context_test.go
@@ -13,8 +13,10 @@ import (
 	"mime/multipart"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"reflect"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -1821,3 +1823,24 @@ func TestContextResetInHandler(t *testing.T) {
 		c.Next()
 	})
 }
+
+func TestRaceParamsContextCopy(t *testing.T) {
+	DefaultWriter = os.Stdout
+	router := Default()
+	nameGroup := router.Group("/:name")
+	var wg sync.WaitGroup
+	wg.Add(2)
+	{
+		nameGroup.GET("/api", func(c *Context) {
+			go func(c *Context, param string) {
+				defer wg.Done()
+				// First assert must be executed after the second request
+				time.Sleep(50 * time.Millisecond)
+				assert.Equal(t, c.Param("name"), param)
+			}(c.Copy(), c.Param("name"))
+		})
+	}
+	performRequest(router, "GET", "/name1/api")
+	performRequest(router, "GET", "/name2/api")
+	wg.Wait()
+}