Mvp 版本讨论

以此为Mvp目标，大家看看是否有要补充的。

```proto

# filename: helloworld.proto

syntax = "proto3";
package grpc.health.v1;

option go_package = "dubbojs/mvp";

message HealthCheckRequest {
string service = 1;
}

message HealthCheckResponse {
enum ServingStatus {
UNKNOWN = 0;
SERVING = 1;
NOT_SERVING = 2;
SERVICE_UNKNOWN = 3; // Used only by the Watch method.
}
ServingStatus status = 1;
}

message HelloRequest {
string name = 1;
}

message HelloReply {
string message = 1;
}

service Mvp {
rpc SayHello (HelloRequest) returns (HelloReply) {}
rpc Check(HealthCheckRequest) returns (HealthCheckResponse);
rpc Watch(HealthCheckRequest) returns (stream HealthCheckResponse);
}

```