Top 20 NuGet concurrency Packages

Sharded actors with managed lifecycle for Akka.NET cluster
Reactive stream support for Akka.NET
Replicated data using CRDT structures
Adds a concept of thread safety to C# and VB so that most threading defects are detected at build-time or in a single-threaded test coverage. Includes a deadlock detection policy and thread dispatching aspects. An official PostSharp pattern library.
Akka.NET is a port of the popular Java/Scala framework Akka to .NET
Provides useful structures for performing efficient concurrent operations. Original Project: https://github.com/etishor/ConcurrencyUtilities, including a port of Java's LongAdder and Striped64 classes
Remote actor support for Akka.NET
Dependency injection support for Akka.NET
You need a Akka.TestKit.* package! Add the one appropriate for the test framework you use instead. For example: Akka.TestKit.Xunit or Akka.TestKit.VsTest. This package only contains base functionality for writing tests for the Akka.NET framework.
Cluster support for Akka.NET
Akka Persistence journal and snapshot store backed by SQL Server database.
Hyperion serializer for Akka.NET
NLog logging adapter for Akka.NET
AutoFac Dependency Injection (DI) support for Akka.NET
TestKit for writing tests for Akka.NET using NUnit.
Persistence actor support for Akka.NET
Serilog logging adapter for Akka.NET.
Distributed publish/subscribe, client and singleton support for Akka.NET cluster
TestKit for writing tests for Akka.NET using xUnit.
Akka.NET Persistence ADO.NET middleware