readme: add scanner example

README.md

@@ -107,6 +107,17 @@ If there is no error, this doesn't mean the result is found, the `res.Hit()` fun
 
 To iterate through the cached items, use the `Scanner` tool:
 
+```go
+scanner := filecache.NewScanner("/path/to/cache/dir")
+
+err := scanner.Scan(func(entry filecache.ScanEntry) error {
+    // Do something with the found entry...
+})
+if err := nil {
+	// Handle the error...
+}
+```
+
 ### Removing the expired items
 
 The expired cache items are removed by the `GarbageCollector`, assigned to the `FileCache` instance.

scanner.go

@@ -9,11 +9,17 @@ import (
 
 // ScanEntry is a scanner hit entry.
 type ScanEntry struct {
-	Key       string
+	// Key is a cache item key.
+	Key string
+
+	// CreatedAt is a cache item created-at timestamp.
 	CreatedAt time.Time
-	Options   *ItemOptions
-	itemPath  string
-	metaPath  string
+
+	// Options are the options of the item stored in the cache.
+	Options *ItemOptions
+
+	itemPath string
+	metaPath string
 }
 
 // ScannerHitFn is a function called on every scanner's hit.