https://mustak.im/grpc-for-asp-net-core-3-0/

Client.cs

using System;
using System.Net.Http;
using System.Threading.Tasks;
using Grpc.Net.Client;
using GrpcDotNetDemoPackage;

namespace Client
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var client = await GetClient();

            var response = await client.SayHelloAsync(new HelloRequest
            {
                Name = "Mustakim"
            });
            
            Console.WriteLine(response.Hello);
        }
        
        private static Task<DemoService.DemoServiceClient> GetClient()
        {
            // This disables HTTPS
            // https://github.com/aspnet/AspNetCore.Docs/issues/13120
            AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);
            var httpClient = new HttpClient
            {
                BaseAddress = new Uri("http://localhost:5000")
            };

            var client = GrpcClient.Create<DemoService.DemoServiceClient>(httpClient);
            return Task.FromResult(client);
        }
    }
}

Client.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <OutputType>Exe</OutputType>
  </PropertyGroup>
  
  <ItemGroup>
    <PackageReference Include="Grpc.Net.Client" Version="0.1.22-pre2" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\Protos\Protos.csproj" />
  </ItemGroup>
</Project>