Use cache interface instead of freecache

cache.go

@@ -1,6 +1,7 @@
 package cache
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"time"
@@ -26,21 +27,36 @@ type Config struct {
 	// Cache fuction called before cache a request, if false, the request is not
 	// cached. If set Method is ignored.
 	Cache func(r *http.Request) bool
+	// GetNotFoundErr is a function that returns the error that signals that the cache entry was not found.
+	// To maintain backwards compatibility, the default value which it returns is freecache.ErrNotFound
+	GetNotFoundErr func() error
 }
 
-func New(cfg *Config, cache *freecache.Cache) echo.MiddlewareFunc {
+func defaultGetNotFoundErr() error {
+	return freecache.ErrNotFound
+}
+
+type Cache interface {
+	Set(key, value []byte, ttl int) error
+	Get(key []byte) ([]byte, error)
+}
+
+func New(cfg *Config, cache Cache) echo.MiddlewareFunc {
 	if cfg == nil {
 		cfg = &Config{}
 	}
 
 	defaults.SetDefaults(cfg)
+	if cfg.GetNotFoundErr == nil {
+		cfg.GetNotFoundErr = defaultGetNotFoundErr
+	}
 	m := &CacheMiddleware{cfg: cfg, cache: cache}
 	return m.Handler
 }
 
 type CacheMiddleware struct {
 	cfg   *Config
-	cache *freecache.Cache
+	cache Cache
 }
 
 func (m *CacheMiddleware) Handler(next echo.HandlerFunc) echo.HandlerFunc {
@@ -59,7 +75,7 @@ func (m *CacheMiddleware) Handler(next echo.HandlerFunc) echo.HandlerFunc {
 			return nil
 		}
 
-		if err != freecache.ErrNotFound {
+		if !errors.Is(err, m.cfg.GetNotFoundErr()) {
 			c.Logger().Errorf("error reading cache: %s", err)
 		}
 
@@ -77,7 +93,7 @@ func (m *CacheMiddleware) Handler(next echo.HandlerFunc) echo.HandlerFunc {
 
 func (m *CacheMiddleware) readCache(key []byte, c echo.Context) error {
 	if m.cfg.Refresh != nil && m.cfg.Refresh(c.Request()) {
-		return freecache.ErrNotFound
+		return m.cfg.GetNotFoundErr()
 	}
 
 	value, err := m.cache.Get(key)