Use DI container to retrieve CollectorRegistry

Author: sanych-sun

src/Prometheus.Client.AspNetCore/Prometheus.Client.AspNetCore.csproj

@@ -1,10 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Description>Middleware for the Prometheus.Client</Description>
-    <Copyright>2018 © Sergey Kuznetsov</Copyright>
+    <Copyright>2020 © Serge K, Oleksandr Poliakov</Copyright>
     <AssemblyTitle>Prometheus.Client.AspNetCore</AssemblyTitle>
-    <VersionPrefix>4.0.0</VersionPrefix>
-    <Authors>Sergey Kuznetsov</Authors>
+    <VersionPrefix>4.1.0</VersionPrefix>
+    <Authors>Serge K, Oleksandr Poliakov</Authors>
     <TargetFrameworks>netstandard2.0;netcoreapp2.2;netstandard2.1;netcoreapp3.1</TargetFrameworks>
     <AssemblyName>Prometheus.Client.AspNetCore</AssemblyName>
     <PackageId>Prometheus.Client.AspNetCore</PackageId>
@@ -33,7 +33,7 @@
     </None>
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Prometheus.Client" Version="4.0.0" />
+    <PackageReference Include="Prometheus.Client" Version="4.1.0" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />

src/Prometheus.Client.AspNetCore/PrometheusExtensions.cs

@@ -2,6 +2,7 @@
 using Prometheus.Client.Collectors;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
+using Prometheus.Client.Collectors.Abstractions;
 
 namespace Prometheus.Client.AspNetCore
 {
@@ -35,6 +36,10 @@ public static IApplicationBuilder UsePrometheusServer(this IApplicationBuilder a
             if (!options.MapPath.StartsWith("/"))
                 throw new ArgumentException($"MapPath '{options.MapPath}' should start with '/'");
 
+            options.CollectorRegistryInstance
+                    ??= (ICollectorRegistry)app.ApplicationServices.GetService(typeof(ICollectorRegistry))
+                    ?? Metrics.DefaultCollectorRegistry;
+
             if (options.UseDefaultCollectors)
                 options.CollectorRegistryInstance.UseDefaultCollectors();
 

src/Prometheus.Client.AspNetCore/PrometheusOptions.cs

@@ -18,9 +18,9 @@ public class PrometheusOptions
         public int? Port { get; set; }
 
         /// <summary>
-        ///     CollectorRegistry intance
+        ///     CollectorRegistry instance.
         /// </summary>
-        public ICollectorRegistry CollectorRegistryInstance { get; set; } = Metrics.DefaultCollectorRegistry;
+        public ICollectorRegistry CollectorRegistryInstance { get; set; }
 
         /// <summary>
         ///     Use default collectors