code: func (me *Cache) WalkItems(cb func(ItemInfo)) {
  	me.mu.Lock()
  	defer me.mu.Unlock()
  	for k, ii := range me.items {
  		cb(ItemInfo{
  			Path:     k,
  			Accessed: ii.Accessed,
  			Size:     ii.Size,
  		})
  	}
  }
docs: // Calls the function for every item known to be in the cache.