✨ Cache middleware: Add flag for e2e headers.

Set flag to prevent e2e headers caching to
be the default behavior of the cache middleware.
This would otherwise change quite a lot the
experience for cache middleware current users.

middleware/cache/cache.go

@@ -153,14 +153,16 @@ func New(config ...Config) fiber.Handler {
 
 		// Store all end-to-end headers
 		// (more: https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1)
-		c.Response().Header.VisitAll(
-			func(key []byte, value []byte) {
-				keyS := string(key)
-				if _, isHopbyHop := ignoreHeaders[keyS]; !isHopbyHop {
-					e.e2eHeaders[keyS] = value
-				}
-			},
-		)
+		if cfg.E2EHeaders {
+			c.Response().Header.VisitAll(
+				func(key []byte, value []byte) {
+					keyS := string(key)
+					if _, isHopbyHop := ignoreHeaders[keyS]; !isHopbyHop {
+						e.e2eHeaders[keyS] = value
+					}
+				},
+			)
+		}
 
 		// default cache expiration
 		expiration := uint64(cfg.Expiration.Seconds())

middleware/cache/cache_test.go

@@ -304,7 +304,9 @@ func Test_CustomExpiration(t *testing.T) {
 
 func Test_AdditionalE2EResponseHeaders(t *testing.T) {
 	app := fiber.New()
-	app.Use(New())
+	app.Use(New(Config{
+		E2EHeaders: true,
+	}))
 
 	app.Get("/", func(c *fiber.Ctx) error {
 		c.Response().Header.Add("X-Foobar", "foobar")

middleware/cache/config.go

@@ -54,6 +54,11 @@ type Config struct {
 
 	// Deprecated, use KeyGenerator instead
 	Key func(*fiber.Ctx) string
+
+	// allows you to store additional headers generated by next middlewares & handler
+	//
+	// Default: false
+	E2EHeaders bool
 }
 
 // ConfigDefault is the default config
@@ -66,6 +71,7 @@ var ConfigDefault = Config{
 		return utils.CopyString(c.Path())
 	},
 	ExpirationGenerator: nil,
+	E2EHeaders:          false,
 	Storage:             nil,
 }