no response cache. manual CacheControl middleware

src/Icons/Controllers/IconsController.cs

@@ -28,7 +28,6 @@ namespace Bit.Icons.Controllers
         }
 
         [HttpGet("{hostname}/icon.png")]
-        [ResponseCache(Duration = 604800 /*7 days*/)]
         public async Task<IActionResult> Get(string hostname)
         {
             if(string.IsNullOrWhiteSpace(hostname) || !hostname.Contains("."))

src/Icons/Startup.cs

@@ -2,8 +2,10 @@
 using Bit.Icons.Services;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Net.Http.Headers;
 
 namespace Bit.Icons
 {
@@ -31,7 +33,6 @@ namespace Bit.Icons
             {
                 options.SizeLimit = iconsSettings.CacheSizeLimit;
             });
-            services.AddResponseCaching();
 
             // Services
             services.AddSingleton<IDomainMappingService, DomainMappingService>();
@@ -50,7 +51,16 @@ namespace Bit.Icons
                 app.UseDeveloperExceptionPage();
             }
 
-            app.UseResponseCaching();
+            app.Use(async (context, next) =>
+            {
+                context.Response.GetTypedHeaders().CacheControl = new CacheControlHeaderValue
+                {
+                    Public = true,
+                    MaxAge = TimeSpan.FromDays(7)
+                };
+                await next();
+            });
+
             app.UseMvc();
         }
     }