public Optional<T> getValue() {
        long now = System.currentTimeMillis();
        long diff = now - this.timestamp;
        if (diff > this.expiryMillis) {
            return Optional.empty();
        }
        return getLastKnownValue();
    }
Gets the value.

<p>Returns empty if the expiry on the last known value has been exceeded.</p>

@return the value
helper/src/main/java/me/lucko/helper/messaging/util/ChannelReceiver.java