akkadotnet/akka.net

using (var system = ActorSystem.Create(_systemName, _config.WithFallback(ClusterClientReceptionist.DefaultConfig())
                                                                       .WithFallback(DistributedPubSub.DefaultConfig())))
            {
                var shardRegion = ClusterSharding.Get(system).Start(
                    nameof(SenderActor),
                    Props.Create<SenderActor>(),
                    ClusterShardingSettings.Create(system).WithRole(Roles.Sharding),
                    new MessageExtractor());

                for (int i = 0; i < 100; i++)
                {
                    Thread.Sleep(2000);
                    shardRegion.Tell(new ShardEnvelope("1", "1", "test" + i));
                }

                system.WhenTerminated.Wait();
            }


public class SenderActor : ReceiveActor
    {
        private readonly IActorRef _mediator = DistributedPubSub.Get(Context.System).Mediator;

        public SenderActor()
        {
            Receive<string>(msg =>
            {
                Console.WriteLine(msg);

                _mediator.Tell(new Publish(Topics.SendMessageTopic, msg));
            });
        }
    }

public class ReceiverActor : ReceiveActor
    {
        private readonly IActorRef _mediator = DistributedPubSub.Get(Context.System).Mediator;

        public ReceiverActor()
        {
            Receive<string>(msg =>
            {
                Console.WriteLine(msg);
            });
        }

        protected override void PreStart()
        {
            base.PreStart();
            _mediator.Tell(new Subscribe(Topics.SendMessageTopic, Self));
        }

        protected override void PostStop()
        {
            _mediator.Tell(new Unsubscribe(Topics.SendMessageTopic, Self));
            base.PostStop();
        }
    }