我正在编写有关gRPC 的教程。当我生成.pb.go文件时，我XXX_*在结构体中得到了某种类型。

这是我的consignment.proto文件：

syntax = "proto3";

package go.micro.srv.consignment;

service ShippingService {
    rpc CreateConsignment(Consignment) returns (Response) {}
}

message Consignment {
    string id = 1;
    string description = 2;
    int32 weight = 3;
    repeated Container containers = 4;
    string vessel_id = 5;
}

message Container {
    string id = 1;
    string customer_id = 2;
    string origin = 3;
    string user_id = 4;
}

message Response {
    bool created = 1;
    Consignment consignment = 2;
}

这是.pb.go文件中的结构。有人可以告诉我为什么XXX我的三种类型struct吗？该结构不应该反映我在自己中定义的内容proto吗？

type Consignment struct {
    Id                   string       `protobuf:"bytes,1,opt,name=id" json:"id,omitempty"`
    Description          string       `protobuf:"bytes,2,opt,name=description" json:"description,omitempty"`
    Weight               int32        `protobuf:"varint,3,opt,name=weight" json:"weight,omitempty"`
    Containers           []*Container `protobuf:"bytes,4,rep,name=containers" json:"containers,omitempty"`
    VesselId             string       `protobuf:"bytes,5,opt,name=vessel_id,json=vesselId" json:"vessel_id,omitempty"`
    XXX_NoUnkeyedLiteral struct{}     `json:"-"`
    XXX_unrecognized     []byte       `json:"-"`
    XXX_sizecache        int32        `json:"-"`
}