remainingDurationForKey method
returns cache entry remaining duration for key.
If cache entry is expired or does not exist, returns negative Duration. You can check Duration.isNegative to check if cache does not exist.
Implementation
Duration remainingDurationForKey(String key) {
final expireDate = _timeoutMap[key];
if (expireDate == null) {
return Duration(milliseconds: -1);
}
return Duration(
milliseconds: expireDate - DateTime.now().millisecondsSinceEpoch);
}