Adding a missed ConfigureAwait(false) within MyGetResponseAsync. Without this the async call invokes the UnitySynchronizationContext which is not needed and also causes incorrect behavior as it then requires the main unity thread to execute pending tasks.

Author: UnityAlex

mcs/class/System/System.Net/HttpWebRequest.cs

@@ -1010,7 +1010,7 @@ async Task<HttpWebResponse> MyGetResponseAsync (CancellationToken cancellationTo
 
 					WebConnection.Debug ($"HWR GET RESPONSE LOOP: Req={ID} Op={operation?.ID} {auth_state.NtlmAuthState}");
 
-					writeStream = await operation.GetRequestStreamInternal ();
+					writeStream = await operation.GetRequestStreamInternal ().ConfigureAwait (false);
 					await writeStream.WriteRequestAsync (cancellationToken).ConfigureAwait (false);
 
 					stream = await operation.GetResponseStream ();