Add support for custom message id. #668

src/DotNetCore.CAP/Internal/ICapPublisher.Default.cs

@@ -63,21 +63,22 @@ namespace DotNetCore.CAP.Internal
                 throw new ArgumentNullException(nameof(name));
             }
 
-            if (headers == null)
+            headers ??= new Dictionary<string, string>();
+
+            if (!headers.ContainsKey(Headers.MessageId))
             {
-                headers = new Dictionary<string, string>();
+                var messageId = SnowflakeId.Default().NextId().ToString();
+                headers.Add(Headers.MessageId, messageId);
             }
-
-            var messageId = SnowflakeId.Default().NextId().ToString();
-            headers.Add(Headers.MessageId, messageId);
-            headers.Add(Headers.MessageName, name);
-            headers.Add(Headers.Type, typeof(T).Name);
-            headers.Add(Headers.SentTime, DateTimeOffset.Now.ToString());
+             
             if (!headers.ContainsKey(Headers.CorrelationId))
             {
-                headers.Add(Headers.CorrelationId, messageId);
+                headers.Add(Headers.CorrelationId, headers[Headers.MessageId]);
                 headers.Add(Headers.CorrelationSequence, 0.ToString());
             }
+            headers.Add(Headers.MessageName, name);
+            headers.Add(Headers.Type, typeof(T).Name);
+            headers.Add(Headers.SentTime, DateTimeOffset.Now.ToString());
 
             var message = new Message(headers, value);