From 64596d538bb0926f12199ab675f2d2c518cb0d1c Mon Sep 17 00:00:00 2001
From: "Chris Ross (ASP.NET)" <chrross@microsoft.com>
Date: Tue, 7 Nov 2017 09:03:49 -0800
Subject: [PATCH] TestServer: Copy the feature collection to mitigate
 multi-threading

---
 src/Microsoft.AspNetCore.TestHost/HttpContextBuilder.cs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Microsoft.AspNetCore.TestHost/HttpContextBuilder.cs b/src/Microsoft.AspNetCore.TestHost/HttpContextBuilder.cs
index 8c69ddd0e9..4617be5308 100644
--- a/src/Microsoft.AspNetCore.TestHost/HttpContextBuilder.cs
+++ b/src/Microsoft.AspNetCore.TestHost/HttpContextBuilder.cs
@@ -110,7 +110,13 @@ namespace Microsoft.AspNetCore.TestHost
             {
                 // Sets HasStarted
                 await _responseFeature.FireOnSendingHeadersAsync();
-                _responseTcs.TrySetResult(_httpContext);
+                // Copy the feature collection so we're not multi-threading on the same collection.
+                var newFeatures = new FeatureCollection();
+                foreach (var pair in _httpContext.Features)
+                {
+                    newFeatures[pair.Key] = pair.Value;
+                }
+                _responseTcs.TrySetResult(new DefaultHttpContext(newFeatures));
             }
         }