What version of gRPC and what language are you using?

gRPC 2.34.1, using .NET Core 3.1.

What operating system (Linux, Windows,...) and version?

Linux and Windows

What runtime / compiler are you using (e.g. python version or version of gcc)

.NET Core SDK 3.1, with the azure-functions-core-tools-3 version 3.0.3160-1

What did you do?

• Start an Azure function that uses gRPC to make a request, running under Linux.
• Invoke the function
• Function hangs

Zip file everything to reproduce using Docker: repro.zip

• docker build -t grpc-repro
• docker run -p 7071:7071 -it grpc-repro
• func start (and wait for the console to show that it's started)
• Browse to http://localhost:7071/api/TestFunction

This is the code that makes the request - it's not expected to work, just exercise gRPC:

private static string MakeRequest()
{
    var marshaller = new Marshaller<string>(Encoding.UTF8.GetBytes, Encoding.UTF8.GetString);
    var method = new Method<string, string>(MethodType.Unary,
        "test-service", "test-method",
        marshaller, marshaller);
    var channel = new Channel("spanner.googleapis.com:443", ChannelCredentials.Insecure);
    var callInvoker = channel.CreateCallInvoker();
            
    return callInvoker.BlockingUnaryCall(method, "spanner.googleapis.com", new CallOptions(), "request");
}

What did you expect to see?

An error of "StatusCode="Unavailable", Detail="failed to connect to all addresses"" due to making a bogus request (deliberately).

What did you see instead?

The function hangs.

Anything else we should know about your project / environment?

• The same code "fails correctly" when running in Windows in the Azure Functions host
• The same code "fails correctly" when running in Linux as a console application
• Using an async call doesn't help
• Real (correct) RPCs fail in the same way