HTTP/2 over TLS is not supported on macOS due to missing ALPN support

If you are working with .NET Core on MacOS, you’ll probably get the following exception:

System.NotSupportedException: HTTP/2 over TLS is not supported on macOS due to missing ALPN support.

This happens because at the moment Kestrel doesn’t support HTTP/2 with TLS on macOS and older Windows versions such as Windows 7. To work around this issue, you have to disable TLS. Open your Program.cs file and update the CreateHostBuilder with the following lines:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.ConfigureKestrel(options =>
            {
                options.ListenLocalhost(5000, o => o.Protocols = HttpProtocols.Http2);
            });
            webBuilder.UseStartup<Startup>();
        });

That’s it! Now you can execute dotnet run command to start your gRPC service.

Enjoy!