Update async process handling

server/Utils/Extensions/ProcessExtensions.cs

@@ -0,0 +1,25 @@
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace PodNoms.Api.Utils.Extensions {
+    public static class ProcessExtensions {
+        /// <summary>
+        /// Waits asynchronously for the process to exit.
+        /// </summary>
+        /// <param name="process">The process to wait for cancellation.</param>
+        /// <param name="cancellationToken">A cancellation token. If invoked, the task will return 
+        /// immediately as canceled.</param>
+        /// <returns>A Task representing waiting for the process to end.</returns>
+        public static Task WaitForExitAsync (this Process process,
+            CancellationToken cancellationToken = default (CancellationToken)) {
+            var tcs = new TaskCompletionSource<object> ();
+            process.EnableRaisingEvents = true;
+            process.Exited += (sender, args) => tcs.TrySetResult (null);
+            if (cancellationToken != default (CancellationToken))
+                cancellationToken.Register (tcs.SetCanceled);
+
+            return tcs.Task;
+        }
+    }
+}