I think use return value easier to understand.

[zoujiaqing]

  import helloworld.helloworld;
  import helloworld.helloworldrpc;
  import grpc;
  import std.stdio;

  auto channel = new Channel("127.0.0.1" , 50051);
  GreeterClient client = new GreeterClient(channel);

  HelloRequest request = new HelloRequest();
  request.name = "test";

  auto reply = client.SayHello(request);
  if(reply !is null)
  {
     writeln(reply.message);
  }

[zhangyuchun]

fixed it.