Feature: [Cache] add ExpirationGenerator for generate custom Expiration (#1618)

* Feature: [Cache] add ExpirationGenerator for generate custom Expiration

* fix: add document and code snippet for README

Co-authored-by: dj <github@djunny.com>

middleware/cache/README.md

@@ -50,6 +50,25 @@ app.Use(cache.New(cache.Config{
 }))
 ```
 
+### Custom Cache Key Or Expiration
+
+```go
+app.Use(New(Config{
+	ExpirationGenerator: func(c *fiber.Ctx, cfg *Config) time.Duration {
+		newCacheTime, _ := strconv.Atoi(c.GetRespHeader("Cache-Time", "600"))
+		return time.Second * time.Duration(newCacheTime)
+	},
+	KeyGenerator: func(c *fiber.Ctx) string {
+		return c.Path()
+	}
+}))
+
+app.Get("/", func(c *fiber.Ctx) error {
+	c.Response().Header.Add("Cache-Time", "6000")
+	return c.SendString("hi")
+})
+```
+
 ### Config
 
 ```go
@@ -84,6 +103,11 @@ type Config struct {
 	// }
 	KeyGenerator func(*fiber.Ctx) string
 
+	// allows you to generate custom Expiration Key By Key, default is Expiration (Optional)
+	//
+	// Default: nil
+	ExpirationGenerator func(*fiber.Ctx, *Config) time.Duration
+
 	// Store is used to store the state of the middleware
 	//
 	// Default: an in memory store for this process only
@@ -103,6 +127,7 @@ var ConfigDefault = Config{
 	KeyGenerator: func(c *fiber.Ctx) string {
 		return utils.CopyString(c.Path())
 	},
+	ExpirationGenerator : nil,
 	Storage:      nil,
 }
 ```

middleware/cache/cache.go

@@ -41,9 +41,8 @@ func New(config ...Config) fiber.Handler {
 
 	var (
 		// Cache settings
-		mux        = &sync.RWMutex{}
-		timestamp  = uint64(time.Now().Unix())
-		expiration = uint64(cfg.Expiration.Seconds())
+		mux       = &sync.RWMutex{}
+		timestamp = uint64(time.Now().Unix())
 	)
 	// Create manager to simplify storage operations ( see manager.go )
 	manager := newManager(cfg.Storage)
@@ -125,6 +124,13 @@ func New(config ...Config) fiber.Handler {
 		e.status = c.Response().StatusCode()
 		e.ctype = utils.CopyBytes(c.Response().Header.ContentType())
 		e.cencoding = utils.CopyBytes(c.Response().Header.Peek(fiber.HeaderContentEncoding))
+
+		// default cache expiration
+		expiration := uint64(cfg.Expiration.Seconds())
+		// Calculate expiration by response header or other setting
+		if cfg.ExpirationGenerator != nil {
+			expiration = uint64(cfg.ExpirationGenerator(c, &cfg).Seconds())
+		}
 		e.exp = ts + expiration
 
 		// For external Storage we store raw body separated

middleware/cache/cache_test.go

@@ -280,6 +280,28 @@ func Test_CustomKey(t *testing.T) {
 	utils.AssertEqual(t, true, called)
 }
 
+func Test_CustomExpiration(t *testing.T) {
+	app := fiber.New()
+	var called bool
+	var newCacheTime int
+	app.Use(New(Config{ExpirationGenerator: func(c *fiber.Ctx, cfg *Config) time.Duration {
+		called = true
+		newCacheTime, _ = strconv.Atoi(c.GetRespHeader("Cache-Time", "600"))
+		return time.Second * time.Duration(newCacheTime)
+	}}))
+
+	app.Get("/", func(c *fiber.Ctx) error {
+		c.Response().Header.Add("Cache-Time", "6000")
+		return c.SendString("hi")
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	_, err := app.Test(req)
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, true, called)
+	utils.AssertEqual(t, 6000, newCacheTime)
+}
+
 func Test_CacheHeader(t *testing.T) {
 	app := fiber.New()
 

middleware/cache/config.go

@@ -39,6 +39,11 @@ type Config struct {
 	// }
 	KeyGenerator func(*fiber.Ctx) string
 
+	// allows you to generate custom Expiration Key By Key, default is Expiration (Optional)
+	//
+	// Default: nil
+	ExpirationGenerator func(*fiber.Ctx, *Config) time.Duration
+
 	// Store is used to store the state of the middleware
 	//
 	// Default: an in memory store for this process only
@@ -60,7 +65,8 @@ var ConfigDefault = Config{
 	KeyGenerator: func(c *fiber.Ctx) string {
 		return utils.CopyString(c.Path())
 	},
-	Storage: nil,
+	ExpirationGenerator: nil,
+	Storage:             nil,
 }
 
 // Helper function to set default values