problem: missing docs for async await

Author: somdoron

docs/async-await.md

@@ -0,0 +1,60 @@
+Async Await
+===========
+
+Since version (4.0.0.239-pre) NetMQ support async/await.
+
+To use async/await feature you need to create a `NetMQRuntime`.
+
+## Example:
+
+```csharp
+async Task ServerAsync()
+{
+    using (var server = new RouterSocket("inproc://async"))
+    {
+        for (int i = 0; i < 1000; i++)
+        {
+            var (routingKey, more) = await server.ReceiveRoutingKeyAsync();
+            var (message, _) = await server.ReceiveFrameStringAsync();
+
+            // TODO: process message
+
+            await Task.Delay(100);
+            server.SendMoreFrame(routingKey);
+            server.SendFrame("Welcome");
+        }
+    }
+}
+
+async Task ClientAsync()
+{
+    using (var client = new DealerSocket("inproc://async"))
+    {
+        for (int i = 0; i < 1000; i++)
+        {
+            client.SendFrame("Hello");
+            var (message, more) = await client.ReceiveFrameStringAsync();
+
+            // TODO: process reply
+
+            await Task.Delay(100);
+        }
+    }
+}
+
+static void Main(string[] args)
+{
+    using (var runtime = new NetMQRuntime())
+    {
+        runtime.Run(ServerAsync(), ClientAsync());
+    }
+}
+```
+
+NetMQRuntime is a wrapper over NetMQPoller, when calling an async function the socket is automatically added to the internal poller.
+NetMQRuntime is also a NetMQScheduler and SyncrhonizationContext, so any awaited function is continuing on the runtime's thread.
+
+NetMQSocket should still be used only within one thread.
+
+`NetMQRuntime.Run` can accept multiple tasks and also a cancellation token.
+`NetMQRuntime.Run` runs until all tasks are completed or cancellation token has been cancelled.

mkdocs.yml

@@ -5,6 +5,7 @@ pages:
 - Introduction: introduction.md
 - Concepts:
   - Receiving and Sending: receiving-sending.md
+  - Async/Await: async-await.md
   - Messages: message.md
   - Transports: transports.md
   - Cleanup: cleanup.md

src/NetMQ.sln

@@ -39,6 +39,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Docs", "Docs", "{FF13931E-D
 		..\docs\timer.md = ..\docs\timer.md
 		..\docs\transports.md = ..\docs\transports.md
 		..\docs\xpub-xsub.md = ..\docs\xpub-xsub.md
+		..\docs\async-await.md = ..\docs\async-await.md
 	EndProjectSection
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "NetMQ", "NetMQ\NetMQ.csproj", "{49C06317-631D-435F-BE51-A26618FBC2C1}"