cache.go
func (c *cache) GetWithExpiration(k string) (interface{}, time.Time, bool) {
	c.mu.RLock()
	// "Inlining" of get and Expired
	item, found := c.items[k]
	if !found {
		c.mu.RUnlock()
		return nil, time.Time{}, false
	}

	if item.Expiration > 0 {
		if time.Now().UnixNano() > item.Expiration {
			c.mu.RUnlock()
			return nil, time.Time{}, false
		}

		// Return the item and the expiration time
		c.mu.RUnlock()
		return item.Object, time.Unix(0, item.Expiration), true
	}

	// If expiration <= 0 (i.e. no expiration time set) then return the item
	// and a zeroed time.Time
	c.mu.RUnlock()
	return item.Object, time.Time{}, true
}
func (c *cache) GetWithExpiration(k string) (interface{}, time.Time, bool) {
	c.mu.RLock()
	// "Inlining" of get and Expired
	item, found := c.items[k]
	if !found {
		c.mu.RUnlock()
		return nil, time.Time{}, false
	}

	if item.Expiration > 0 {
		if time.Now().UnixNano() > item.Expiration {
			c.mu.RUnlock()
			return nil, time.Time{}, false
		}

		// Return the item and the expiration time
		c.mu.RUnlock()
		return item.Object, time.Unix(0, item.Expiration), true
	}

	// If expiration <= 0 (i.e. no expiration time set) then return the item
	// and a zeroed time.Time
	c.mu.RUnlock()
	return item.Object, time.Time{}, true
}
// GetWithExpiration returns an item and its expiration time from the cache.
// It returns the item or nil, the expiration time if one is set (if the item
// never expires a zero value for time.Time is returned), and a bool indicating
// whether the key was found.