Cleaned up code smells.

Made fields readonly when possible.

Changed message for exception regarding argument to be correct.

src/GameServiceWarden.Host/Modules/ModuleLoadContext.cs

@@ -6,7 +6,7 @@ namespace GameServiceWarden.Host.Modules
 {
     class ModuleLoadContext : AssemblyLoadContext
     {
-        private AssemblyDependencyResolver dependencyResolver;
+        private readonly AssemblyDependencyResolver dependencyResolver;
 
         public ModuleLoadContext(string path) {
             dependencyResolver = new AssemblyDependencyResolver(path);

src/GameServiceWarden.Host/Modules/ServiceGateway.cs

@@ -6,7 +6,7 @@ namespace GameServiceWarden.Host.Modules
 {
     public class ServiceGateway
     {
-        private string dataDirectory;
+        private readonly string dataDirectory;
         private const string SERVICE_NAME = "Service Name";
         private const string ASSEMBLY_NAME = "Assembly Name";
         private const string MODULE_NAME = "Module Name";

src/GameServiceWarden.Host/Modules/ServiceInfo.cs

@@ -22,7 +22,7 @@ namespace GameServiceWarden.Host.Modules
         /// </summary>
         private volatile string serviceName; //thread-safe(?)
         public Stream ServiceConsoleStream { get; private set; } // Thread safe.
-        private object controlLock = new object();
+        private readonly object controlLock = new object();
         private volatile ServiceState state;
         private readonly IGameService service;
         private readonly string assemblyName;
@@ -32,7 +32,7 @@ namespace GameServiceWarden.Host.Modules
 
         public ServiceInfo(IGameService service, string moduleName, string assemblyName)
         {
-            this.service = service ?? throw new ArgumentNullException("serviceable");
+            this.service = service ?? throw new ArgumentNullException("service");
             this.moduleName = moduleName ?? throw new ArgumentNullException("moduleName");
             this.assemblyName = assemblyName ?? throw new ArgumentNullException("assemblyName");
             this.service.StateChangeEvent += OnServiceStateChange;