Use async main in dotnet-watch

src/Microsoft.DotNet.Watcher.Tools/Microsoft.DotNet.Watcher.Tools.csproj

@@ -3,6 +3,7 @@
   <Import Project="..\..\build\common.props" />
 
   <PropertyGroup>
+    <LangVersion>7.1</LangVersion>
     <TargetFramework>netcoreapp2.0</TargetFramework>
     <AssemblyName>dotnet-watch</AssemblyName>
     <OutputType>exe</OutputType>

src/Microsoft.DotNet.Watcher.Tools/Program.cs

@@ -31,15 +31,21 @@ namespace Microsoft.DotNet.Watcher
             _reporter = CreateReporter(verbose: true, quiet: false, console: _console);
         }
 
-        public static int Main(string[] args)
+        public static async Task<int> Main(string[] args)
         {
-            DebugHelper.HandleDebugSwitch(ref args);
+            try
-            using (var program = new Program(PhysicalConsole.Singleton, Directory.GetCurrentDirectory()))
             {
-                return program
+                DebugHelper.HandleDebugSwitch(ref args);
-                    .RunAsync(args)
+                using (var program = new Program(PhysicalConsole.Singleton, Directory.GetCurrentDirectory()))
-                    .GetAwaiter()
+                {
-                    .GetResult();
+                    return await program.RunAsync(args);
+                }
+            }
+            catch (Exception ex)
+            {
+                Console.Error.WriteLine("Unexpected error:");
+                Console.Error.WriteLine(ex.ToString());
+                return 1;
             }
         }
 
@@ -200,7 +206,6 @@ namespace Microsoft.DotNet.Watcher
         private static IReporter CreateReporter(bool verbose, bool quiet, IConsole console)
             => new PrefixConsoleReporter(console, verbose || CliContext.IsGlobalVerbose(), quiet);
 
-
         private string NormalizePath(string path)
         {
             if (path == null || Path.IsPathRooted(path))