feat(batch18): implement group-a server core helpers

dotnet/src/ZB.MOM.NatsNet.Server/NatsServer.Lifecycle.cs

@@ -178,7 +178,13 @@ public sealed partial class NatsServer
     /// Returns true if the goroutine was started, false if the server is already stopped.
     /// Mirrors Go <c>Server.startGoRoutine(f)</c>.
     /// </summary>
-    internal bool StartGoRoutine(Action f)
+    internal bool StartGoRoutine(Action f) => StartGoRoutine(f, []);
+
+    /// <summary>
+    /// Starts a background Task with goroutine labels.
+    /// Mirrors Go <c>Server.startGoRoutine(f, tags...)</c>.
+    /// </summary>
+    internal bool StartGoRoutine(Action f, params IReadOnlyDictionary<string, string>[] tags)
     {
         lock (_grMu)
         {
@@ -186,13 +192,41 @@ public sealed partial class NatsServer
             _grWg.Add(1);
             Task.Run(() =>
             {
-                try { f(); }
+                try
+                {
+                    SetGoRoutineLabels(tags);
+                    f();
+                }
                 finally { _grWg.Done(); }
             });
             return true;
         }
     }
 
+    /// <summary>
+    /// Optional test-only sink used to observe goroutine labels during unit tests.
+    /// </summary>
+    internal static Action<IReadOnlyList<KeyValuePair<string, string>>>? SetGoRoutineLabelsHookForTest { get; set; }
+
+    /// <summary>
+    /// Sets goroutine labels for diagnostics when tags are present.
+    /// Mirrors Go <c>setGoRoutineLabels</c>.
+    /// </summary>
+    internal static void SetGoRoutineLabels(params IReadOnlyDictionary<string, string>[] tags)
+    {
+        var labels = new List<KeyValuePair<string, string>>();
+        foreach (var tag in tags)
+        {
+            foreach (var pair in tag)
+            {
+                labels.Add(new KeyValuePair<string, string>(pair.Key, pair.Value));
+            }
+        }
+
+        if (labels.Count > 0)
+            SetGoRoutineLabelsHookForTest?.Invoke(labels);
+    }
+
     // =========================================================================
     // Client / connection management (features 3081–3084)
     // =========================================================================