New expire extension for delegates.
Set a time to that key expire when set.
var str: String? by string().expire(5) // when set, will expire in 5 seconds**Time in seconds
New withExpire extension for delegate
Pair with the time and expiration time of that key.
var str: Pair<String, Int> by string("A default string").withExpire()
str = "New string expiring in 30 seconds" to 30**Time in seconds
**Expire time can return -2 if the key does not exist or -1 if the key exists but has no associated expire.