deprecate timeout middleware

Author: aldas

CHANGELOG.md

@@ -1,5 +1,118 @@
 # Changelog
 
+## v4.15.0 - TBD
+
+**DEPRECATION NOTICE** Timeout Middleware Deprecated - Use ContextTimeout Instead
+
+The `middleware.Timeout` middleware has been **deprecated** due to fundamental architectural issues that cause
+data races. Use `middleware.ContextTimeout` or `middleware.ContextTimeoutWithConfig` instead.
+
+**Why is this being deprecated?**
+
+The Timeout middleware manipulates response writers across goroutine boundaries, which causes data races that
+cannot be reliably fixed without a complete architectural redesign. The middleware:
+
+- Swaps the response writer using `http.TimeoutHandler`
+- Must be the first middleware in the chain (fragile constraint)
+- Can cause races with other middleware (Logger, metrics, custom middleware)
+- Has been the source of multiple race condition fixes over the years
+
+**What should you use instead?**
+
+The `ContextTimeout` middleware (available since v4.12.0) provides timeout functionality using Go's standard
+context mechanism. It is:
+
+- Race-free by design
+- Can be placed anywhere in the middleware chain
+- Simpler and more maintainable
+- Compatible with all other middleware
+
+**Migration Guide:**
+
+```go
+// Before (deprecated):
+e.Use(middleware.Timeout())
+
+// After (recommended):
+e.Use(middleware.ContextTimeout(30 * time.Second))
+```
+
+With configuration:
+```go
+// Before (deprecated):
+e.Use(middleware.TimeoutWithConfig(middleware.TimeoutConfig{
+    Timeout: 30 * time.Second,
+    Skipper: func(c echo.Context) bool {
+        return c.Path() == "/health"
+    },
+}))
+
+// After (recommended):
+e.Use(middleware.ContextTimeoutWithConfig(middleware.ContextTimeoutConfig{
+    Timeout: 30 * time.Second,
+    Skipper: func(c echo.Context) bool {
+        return c.Path() == "/health"
+    },
+}))
+```
+
+**Important Behavioral Differences:**
+
+1. **Handler cooperation required**: With ContextTimeout, your handlers must check `context.Done()` for cooperative
+   cancellation. The old Timeout middleware would send a 503 response regardless of handler cooperation, but had
+   data race issues.
+
+2. **Error handling**: ContextTimeout returns errors through the standard error handling flow. Handlers that receive
+   `context.DeadlineExceeded` should handle it appropriately:
+
+```go
+e.GET("/long-task", func(c echo.Context) error {
+    ctx := c.Request().Context()
+
+    // Example: database query with context
+    result, err := db.QueryContext(ctx, "SELECT * FROM large_table")
+    if err != nil {
+        if errors.Is(err, context.DeadlineExceeded) {
+            // Handle timeout
+            return echo.NewHTTPError(http.StatusServiceUnavailable, "Request timeout")
+        }
+        return err
+    }
+
+    return c.JSON(http.StatusOK, result)
+})
+```
+
+3. **Background tasks**: For long-running background tasks, use goroutines with context:
+
+```go
+e.GET("/async-task", func(c echo.Context) error {
+    ctx := c.Request().Context()
+
+    resultCh := make(chan Result, 1)
+    errCh := make(chan error, 1)
+
+    go func() {
+        result, err := performLongTask(ctx)
+        if err != nil {
+            errCh <- err
+            return
+        }
+        resultCh <- result
+    }()
+
+    select {
+    case result := <-resultCh:
+        return c.JSON(http.StatusOK, result)
+    case err := <-errCh:
+        return err
+    case <-ctx.Done():
+        return echo.NewHTTPError(http.StatusServiceUnavailable, "Request timeout")
+    }
+})
+```
+
+
 ## v4.14.0 - 2025-12-11
 
 `middleware.Logger` has been deprecated. For request logging, use `middleware.RequestLogger` or

middleware/context_timeout.go

@@ -11,6 +11,39 @@ import (
 	"github.com/labstack/echo/v4"
 )
 
+// ContextTimeout Middleware
+//
+// ContextTimeout provides request timeout functionality using Go's context mechanism.
+// It is the recommended replacement for the deprecated Timeout middleware.
+//
+//
+// Basic Usage:
+//
+//	e.Use(middleware.ContextTimeout(30 * time.Second))
+//
+// With Configuration:
+//
+//	e.Use(middleware.ContextTimeoutWithConfig(middleware.ContextTimeoutConfig{
+//	    Timeout: 30 * time.Second,
+//	    Skipper: middleware.DefaultSkipper,
+//	}))
+//
+// Handler Example:
+//
+//	e.GET("/task", func(c echo.Context) error {
+//	    ctx := c.Request().Context()
+//
+//	    result, err := performTaskWithContext(ctx)
+//	    if err != nil {
+//	        if errors.Is(err, context.DeadlineExceeded) {
+//	            return echo.NewHTTPError(http.StatusServiceUnavailable, "timeout")
+//	        }
+//	        return err
+//	    }
+//
+//	    return c.JSON(http.StatusOK, result)
+//	})
+
 // ContextTimeoutConfig defines the config for ContextTimeout middleware.
 type ContextTimeoutConfig struct {
 	// Skipper defines a function to skip middleware.

middleware/timeout.go

@@ -59,6 +59,12 @@ import (
 //
 
 // TimeoutConfig defines the config for Timeout middleware.
+//
+// Deprecated: Use ContextTimeoutConfig with ContextTimeout or ContextTimeoutWithConfig instead.
+// The Timeout middleware has architectural issues that cause data races due to response writer
+// manipulation across goroutines. It must be the first middleware in the chain, making it fragile.
+// The ContextTimeout middleware provides timeout functionality using Go's context mechanism,
+// which is race-free and can be placed anywhere in the middleware chain.
 type TimeoutConfig struct {
 	// Skipper defines a function to skip middleware.
 	Skipper Skipper
@@ -89,11 +95,38 @@ var DefaultTimeoutConfig = TimeoutConfig{
 
 // Timeout returns a middleware which returns error (503 Service Unavailable error) to client immediately when handler
 // call runs for longer than its time limit. NB: timeout does not stop handler execution.
+//
+// Deprecated: Use ContextTimeout instead. This middleware has known data race issues due to response writer
+// manipulation. See https://github.com/labstack/echo/blob/master/middleware/context_timeout.go for the
+// recommended alternative.
+//
+// Example migration:
+//
+//	// Before:
+//	e.Use(middleware.Timeout())
+//
+//	// After:
+//	e.Use(middleware.ContextTimeout(30 * time.Second))
 func Timeout() echo.MiddlewareFunc {
 	return TimeoutWithConfig(DefaultTimeoutConfig)
 }
 
 // TimeoutWithConfig returns a Timeout middleware with config or panics on invalid configuration.
+//
+// Deprecated: Use ContextTimeoutWithConfig instead. This middleware has architectural data race issues.
+// See the ContextTimeout middleware for a race-free alternative that uses Go's context mechanism.
+//
+// Example migration:
+//
+//	// Before:
+//	e.Use(middleware.TimeoutWithConfig(middleware.TimeoutConfig{
+//		Timeout: 30 * time.Second,
+//	}))
+//
+//	// After:
+//	e.Use(middleware.ContextTimeoutWithConfig(middleware.ContextTimeoutConfig{
+//		Timeout: 30 * time.Second,
+//	}))
 func TimeoutWithConfig(config TimeoutConfig) echo.MiddlewareFunc {
 	mw, err := config.ToMiddleware()
 	if err != nil {
@@ -103,6 +136,8 @@ func TimeoutWithConfig(config TimeoutConfig) echo.MiddlewareFunc {
 }
 
 // ToMiddleware converts Config to middleware or returns an error for invalid configuration
+//
+// Deprecated: Use ContextTimeoutConfig.ToMiddleware instead.
 func (config TimeoutConfig) ToMiddleware() (echo.MiddlewareFunc, error) {
 	if config.Skipper == nil {
 		config.Skipper = DefaultTimeoutConfig.Skipper