DrainXXX options for nats broker and subscriber

options.go

@@ -6,8 +6,20 @@ import (
 )
 
 type optionsKey struct{}
+type drainConnectionKey struct{}
+type drainSubscriptionKey struct{}
 
 // Options accepts nats.Options
 func Options(opts nats.Options) broker.Option {
 	return setBrokerOption(optionsKey{}, opts)
 }
+
+// DrainConnection will drain subscription on close
+func DrainConnection() broker.Option {
+	return setBrokerOption(drainConnectionKey{}, true)
+}
+
+// DrainSubscription will drain pending messages when unsubscribe
+func DrainSubscription() broker.SubscribeOption {
+	return setSubscribeOption(drainSubscriptionKey{}, true)
+}