remove some class from Abstraction namespce to Internal.

src/DotNetCore.CAP/Abstractions/ConsumerInvokerContext.cs

-using System;
-
-namespace DotNetCore.CAP.Abstractions
-{
-    /// <summary>
-    /// a context of consumer invoker.
-    /// </summary>
-    public class ConsumerInvokerContext
-    {
-        public ConsumerInvokerContext(ConsumerContext consumerContext)
-        {
-            ConsumerContext = consumerContext ??
-                              throw new ArgumentNullException(nameof(consumerContext));
-        }
-
-        public ConsumerContext ConsumerContext { get; set; }
-
-        public IConsumerInvoker Result { get; set; }
-    }
-}
\ No newline at end of file

src/DotNetCore.CAP/Abstractions/ConsumerContext.cs → src/DotNetCore.CAP/Internal/ConsumerContext.cs

 using System;
 
-namespace DotNetCore.CAP.Abstractions
+namespace DotNetCore.CAP.Internal
 {
     /// <summary>
     /// A context for consumers, it used to be provider wrapper of method description and received message.

src/DotNetCore.CAP/Internal/ConsumerExecutedResult.cs

+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace DotNetCore.CAP.Internal
+{
+    public class ConsumerExecutedResult
+    {
+        public ConsumerExecutedResult(object result, string msgId, string callbackName)
+        {
+            Result = result;
+            MessageId = msgId;
+            CallbackName = callbackName;
+        }
+
+        public object Result { get; set; }
+
+        public string MessageId { get; set; }
+
+        public string CallbackName { get; set; }
+    }
+}

src/DotNetCore.CAP/Abstractions/ConsumerExecutorDescriptor.cs → src/DotNetCore.CAP/Internal/ConsumerExecutorDescriptor.cs

 using System.Reflection;
+using DotNetCore.CAP.Abstractions;
 
-namespace DotNetCore.CAP.Abstractions
+namespace DotNetCore.CAP.Internal
 {
     /// <summary>
     /// A descriptor of user definition method.

src/DotNetCore.CAP/Abstractions/IConsumerInvoker.cs → src/DotNetCore.CAP/Internal/IConsumerInvoker.cs

 using System.Threading.Tasks;
+using DotNetCore.CAP.Abstractions;
 
-namespace DotNetCore.CAP.Abstractions
+namespace DotNetCore.CAP.Internal
 {
     /// <summary>
     /// Perform user definition method of consumers.
@@ -8,8 +9,9 @@ namespace DotNetCore.CAP.Abstractions
     public interface IConsumerInvoker
     {
         /// <summary>
-        /// begin to invoke method.
+        /// Invoke consumer method whit consumer context.
         /// </summary>
-        Task InvokeAsync();
+        /// <param name="context">consumer execute context</param>
+        Task<ConsumerExecutedResult> InvokeAsync(ConsumerContext context);
     }
 }
\ No newline at end of file

src/DotNetCore.CAP/Abstractions/IConsumerServiceSelector.cs → src/DotNetCore.CAP/Internal/IConsumerServiceSelector.cs

 using System.Collections.Generic;
 
-namespace DotNetCore.CAP.Abstractions
+namespace DotNetCore.CAP.Internal
 {
     /// <summary>
     /// Defines an interface for selecting an consumer service method to invoke for the current message.