Add ${aspnet-traceidentifier} (ASP.NET Core only)

NLog.Web.AspNetCore/LayoutRenderers/Class.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using NLog.LayoutRenderers;
+
+namespace NLog.Web.LayoutRenderers
+{
+    /// <summary>
+    /// Print the TraceIdentifier
+    /// </summary>
+    /// <remarks>.NET Core Only</remarks>
+    [LayoutRenderer("aspnet-traceidentifier")]
+    public class AspNetTraceIdentifierLayoutRenderer : AspNetLayoutRendererBase
+    {
+        /// <inheritdoc />
+        protected override void DoAppend(StringBuilder builder, LogEventInfo logEvent)
+        {
+            var context = HttpContextAccessor.HttpContext;
+
+            builder.Append(context.TraceIdentifier);
+        }
+    }
+}