(draft) Improving cache behavior for first entry

Resolves gofiber#3072

Author: brunodmartins

Diff for: middleware/cache/cache.go

@@ -123,13 +123,13 @@ func New(config ...Config) fiber.Handler {
 		}
 
 		// Check if entry is expired
-		if e.exp != 0 && ts >= e.exp {
+		if e != nil && e.exp != 0 && ts >= e.exp {
 			deleteKey(key)
 			if cfg.MaxBytes > 0 {
 				_, size := heap.remove(e.heapidx)
 				storedBytes -= size
 			}
-		} else if e.exp != 0 && !hasRequestDirective(c, noCache) {
+		} else if e != nil && e.exp != 0 && !hasRequestDirective(c, noCache) {
 			// Separate body value to avoid msgp serialization
 			// We can store raw bytes with Storage 👍
 			if cfg.Storage != nil {
@@ -193,6 +193,7 @@ func New(config ...Config) fiber.Handler {
 			}
 		}
 
+		e = manager.acquire()
 		// Cache response
 		e.body = utils.CopyBytes(c.Response().Body())
 		e.status = c.Response().StatusCode()

Diff for: middleware/cache/heap.go

@@ -15,7 +15,7 @@ type heapEntry struct {
 // elements in constant time. It does so by handing out special indices
 // and tracking entry movement.
 //
-// indexdedHeap is used for quickly finding entries with the lowest
+// indexedHeap is used for quickly finding entries with the lowest
 // expiration timestamp and deleting arbitrary entries.
 type indexedHeap struct {
 	// Slice the heap is built on

Diff for: middleware/cache/manager.go

@@ -83,8 +83,7 @@ func (m *manager) get(key string) *item {
 		return it
 	}
 	if it, _ = m.memory.Get(key).(*item); it == nil { //nolint:errcheck // We store nothing else in the pool
-		it = m.acquire()
-		return it
+		return nil
 	}
 	return it
 }