Fix error when HedgingDelay is null (#1351)

Author: JamesNK

src/Grpc.Net.Client/Internal/GrpcMethodInfo.cs

@@ -101,7 +101,7 @@ internal static HedgingPolicyInfo CreateHedgingPolicy(HedgingPolicy h)
             {
                 throw new InvalidOperationException("Hedging policy max attempts must be greater than 1.");
             }
-            if (!(h.HedgingDelay >= TimeSpan.Zero))
+            if (h.HedgingDelay != null && h.HedgingDelay < TimeSpan.Zero)
             {
                 throw new InvalidOperationException("Hedging policy delay must be equal or greater than zero.");
             }

test/FunctionalTests/Client/HedgingTests.cs

@@ -39,9 +39,10 @@ namespace Grpc.AspNetCore.FunctionalTests.Client
     [TestFixture]
     public class HedgingTests : FunctionalTestBase
     {
+        [TestCase(null)]
         [TestCase(0)]
         [TestCase(20)]
-        public async Task Unary_ExceedAttempts_Failure(int hedgingDelay)
+        public async Task Unary_ExceedAttempts_Failure(int? hedgingDelay)
         {
             Task<DataMessage> UnaryFailure(DataMessage request, ServerCallContext context)
             {
@@ -57,7 +58,10 @@ Task<DataMessage> UnaryFailure(DataMessage request, ServerCallContext context)
             // Arrange
             var method = Fixture.DynamicGrpc.AddUnaryMethod<DataMessage, DataMessage>(UnaryFailure);
 
-            var channel = CreateChannel(serviceConfig: ServiceConfigHelpers.CreateHedgingServiceConfig(maxAttempts: 5, hedgingDelay: TimeSpan.FromMilliseconds(hedgingDelay)));
+            var delay = (hedgingDelay == null)
+                ? (TimeSpan?)null
+                : TimeSpan.FromMilliseconds(hedgingDelay.Value);
+            var channel = CreateChannel(serviceConfig: ServiceConfigHelpers.CreateHedgingServiceConfig(maxAttempts: 5, hedgingDelay: delay));
 
             var client = TestClientFactory.Create(channel, method);
 

test/Shared/ServiceConfigHelpers.cs

@@ -76,7 +76,7 @@ public static ServiceConfig CreateHedgingServiceConfig(
             var hedgingPolicy = new HedgingPolicy
             {
                 MaxAttempts = maxAttempts ?? 5,
-                HedgingDelay = hedgingDelay ?? TimeSpan.Zero
+                HedgingDelay = hedgingDelay
             };
 
             if (nonFatalStatusCodes != null)