feat(timeout): unify and enhance timeout middleware

- Combine classic context-based timeout with a Goroutine + channel approach
- Support custom error list without additional parameters
- Return fiber.ErrRequestTimeout for timeouts or listed errors

middleware/timeout/timeout.go

@@ -8,23 +8,51 @@ import (
 	"github.com/gofiber/fiber/v3"
 )
 
-// New implementation of timeout middleware. Set custom errors(context.DeadlineExceeded vs) for get fiber.ErrRequestTimeout response.
-func New(h fiber.Handler, t time.Duration, tErrs ...error) fiber.Handler {
-	return func(ctx fiber.Ctx) error {
-		timeoutContext, cancel := context.WithTimeout(ctx.Context(), t)
+// New sets a request timeout, runs the handler in a separate Goroutine, and
+// returns fiber.ErrRequestTimeout when the timeout or any of the specified errors occur.
+func New(h fiber.Handler, timeout time.Duration, tErrs ...error) fiber.Handler {
+	return func(c fiber.Ctx) error {
+		// Create a context with a timeout
+		ctx, cancel := context.WithTimeout(c.Context(), timeout)
 		defer cancel()
-		ctx.SetContext(timeoutContext)
-		if err := h(ctx); err != nil {
-			if errors.Is(err, context.DeadlineExceeded) {
+
+		// Attach the new context to the Fiber context
+		c.SetContext(ctx)
+
+		// Channel to capture the handler's result (error)
+		done := make(chan error, 1)
+
+		// Execute the handler in a separate Goroutine
+		go func() {
+			done <- h(c)
+		}()
+
+		// Wait for either the timeout or the handler to finish
+		select {
+		case <-ctx.Done():
+			// Triggered if the timeout occurs or the context is canceled
+			if errors.Is(ctx.Err(), context.DeadlineExceeded) {
 				return fiber.ErrRequestTimeout
 			}
-			for i := range tErrs {
-				if errors.Is(err, tErrs[i]) {
+			// For other context cancellations, we can still treat them the same
+			return fiber.ErrRequestTimeout
+
+		case err := <-done:
+			// If the handler returned an error
+			if err != nil {
+				// Check if it's a deadline exceeded error
+				if errors.Is(err, context.DeadlineExceeded) {
 					return fiber.ErrRequestTimeout
 				}
+				// Check against any custom errors in the list
+				for _, timeoutErr := range tErrs {
+					if errors.Is(err, timeoutErr) {
+						return fiber.ErrRequestTimeout
+					}
+				}
 			}
+			// Otherwise, return the handler's error or nil
 			return err
 		}
-		return nil
 	}
 }