get method
Retrieves a value from the cache.
Returns the cached value if found and not expired, null otherwise.
Implementation
dynamic get(String key) {
final entry = _cache[key];
if (entry == null) return null;
if (entry.isExpired) {
_cache.remove(key);
return null;
}
// Update access time for LRU
entry.updateAccessTime();
return entry.value;
}