chore: not use new for register

Author: phnx47

src/Prometheus.Client.DependencyInjection/Prometheus.Client.DependencyInjection.csproj

@@ -3,7 +3,7 @@
     <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
     <Copyright>2020 © Serge K, Oleksandr Poliakov</Copyright>
     <AssemblyTitle>Prometheus.Client.DependencyInjection</AssemblyTitle>
-    <VersionPrefix>0.4.0</VersionPrefix>
+    <VersionPrefix>0.5.0</VersionPrefix>
     <Authors>Serge K, Oleksandr Poliakov</Authors>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>../../Prometheus.Client.DependencyInjection.snk</AssemblyOriginatorKeyFile>

src/Prometheus.Client.DependencyInjection/ServiceCollectionExtensions.cs

@@ -6,17 +6,18 @@ namespace Prometheus.Client.DependencyInjection
     public static class ServiceCollectionExtensions
     {
         /// <summary>
-        /// Add IMetricFactory and ICollectorRegistry into service collection
+        ///     Add IMetricFactory and ICollectorRegistry into service collection
         /// </summary>
         /// <param name="services">Service collection</param>
         public static IServiceCollection AddMetricFactory(this IServiceCollection services)
         {
-            services.AddMetricFactory(new CollectorRegistry());
+            services.AddSingleton<ICollectorRegistry, CollectorRegistry>();
+            services.AddSingleton<IMetricFactory, MetricFactory>();
             return services;
         }
 
         /// <summary>
-        /// Add IMetricFactory and ICollectorRegistry into service collection
+        ///     Add IMetricFactory and ICollectorRegistry into service collection
         /// </summary>
         /// <param name="services">Service collection</param>
         /// <param name="collectorRegistry">Explicit collector registry to use</param>