Remove System.Runtime.Loader dependency to enable net461 support. Use IApplicationLifetime instead of AssemblyLoadContext.Default.Unloading.

src/Microsoft.AspNetCore.NodeServices/Configuration/NodeServicesOptions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Threading;
 using Microsoft.AspNetCore.NodeServices.HostingModels;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.DependencyInjection;
@@ -42,6 +43,12 @@ namespace Microsoft.AspNetCore.NodeServices
                 EnvironmentVariables["NODE_ENV"] = hostEnv.IsDevelopment() ? "development" : "production"; // De-facto standard values for Node
             }
 
+            var applicationLifetime = serviceProvider.GetService<IApplicationLifetime>();
+            if (applicationLifetime != null)
+            {
+                ApplicationStoppingToken = applicationLifetime.ApplicationStopping;
+            }
+
             // If the DI system gives us a logger, use it. Otherwise, set up a default one.
             var loggerFactory = serviceProvider.GetService<ILoggerFactory>();
             NodeInstanceOutputLogger = loggerFactory != null
@@ -93,5 +100,10 @@ namespace Microsoft.AspNetCore.NodeServices
         /// Specifies the maximum duration, in milliseconds, that your .NET code should wait for Node.js RPC calls to return.
         /// </summary>
         public int InvocationTimeoutMilliseconds { get; set; }
+
+        /// <summary>
+        /// A token that indicates when the host application is stopping.
+        /// </summary>
+        public CancellationToken ApplicationStoppingToken { get; set; }
     }
 }