4. 上下文映射图：Context Map 概念、上下游关系、共享内核、客户方-供应方模式

// 下游订单服务中的防腐层适配器
package adapter

type UserServiceClient interface {
    GetUser(ctx context.Context, userID string) (*UserDTO, error)
}

// 防腐层：将上游的 UserDTO 转换为订单上下文中的 UserVO
type UserAdapter struct {
    client UserServiceClient
}

func (a *UserAdapter) GetUser(ctx context.Context, userID string) (*UserVO, error) {
    dto, err := a.client.GetUser(ctx, userID)
    if err != nil {
        return nil, fmt.Errorf("user adapter: %w", err)
    }
    return &UserVO{
        ID:   dto.ID,
        Name: dto.Name,
    }, nil
}

// payment.proto（供应方定义）
syntax = "proto3";
package payment;

service PaymentService {
    rpc Charge(ChargeRequest) returns (ChargeResponse);
}

message ChargeRequest {
    string order_id = 1;
    double amount = 2;
    string currency = 3;
}

message ChargeResponse {
    string transaction_id = 1;
    bool success = 2;
}

// 客户方（订单服务）调用代码
package infrastructure

import (
    pb "github.com/company/payment-proto/gen/go/payment"
)

type PaymentClient struct {
    client pb.PaymentServiceClient
}

func (c *PaymentClient) Charge(ctx context.Context, req *pb.ChargeRequest) (*pb.ChargeResponse, error) {
    return c.client.Charge(ctx, req)
}