我正在学习依赖注入，并希望在gRPC项目中使用它，但我不确定如何做到这一点。我有这个gRPC服务

service UserService {
    rpc GetUser(GetUserRequest) returns (User);
}

message GetUserRequest {
    oneof prop {
        string id = 1;
        string email = 2;
        string phoneNumber = 3;
    } 
}

message User {
    string firstName = 1;
    string lastName = 2;                                            
    ...
}

然后在main函数中定义GetUser并初始化服务器
main.go

package main

import (
    pb "proto/user/go"
    "context"
    "net"
    "fmt"
)

type Server struct {
    pb.UserServiceServer
}

func (s *Server) GetUser(ctx context.Context, req *pb.GetUserRequest) (*pb.User, error) {
    var user pb.User
    var err error
    switch req.Prop.(type) {
    case *pb.GetUserRequest_Email:
        user, err = GetUserByEmail(req.GetEmail())
    case *pb.GetUserRequest_Id:
        user, err = GetUserById(req.GetId())
    case *pb.GetUserRequest_PhoneNumber:
        user, err = GetUserByPhoneNumber(req.GetPhoneNumber())
    }
    return &user, err
}

func main() {
    lis, err := net.Listen("tcp", ":50051")
    if err != nil {
        fmt.Println("Failed to listen for incoming requests")
    }
    s := grpc.NewServer()
    cs := Server{}
    pb.RegisterUserServiceServer(s, cs)
    err = s.Serve(lis)
    if err != nil {
        fmt.Println("Failed to start server: ", err)
    }
}

GetUserByEmail、GetUserById和GetUserByPhoneNumber位于另一个封装中
user/get_user.go

func GetUserById(id string) (pb.User, error) {
    // call the database to get the user
}

所以我的问题是，为了使测试GetUserByEmail，GetUserById和GetUserByPhoneNumber更容易，我必须依赖注入数据库连接，我不知道最好的方法是什么。我的第一个想法是在Server结构体中添加一个名为db的字段，然后在GetUser中将其传递给函数，使其看起来像这样。

type Server struct {
    pb.UserServiceServer
    db *dynamodb.Client
}

func (s *Server) GetUser(ctx context.Context, req *pb.GetUserRequest) (*pb.User, error) {
    var user pb.User
    var err error
    switch req.Prop.(type) {
    case *pb.GetUserRequest_Email:
        user, err = GetUserByEmail(req.GetEmail(), s.db)
    case *pb.GetUserRequest_Id:
        user, err = GetUserById(req.GetId(), s.db)
    case *pb.GetUserRequest_PhoneNumber:
        user, err = GetUserByPhoneNumber(req.GetPhoneNumber(), s.db)
    }
    return &user, err
}

我觉得使用参数传递数据库不是一个好的做法，但我可能是错的。任何帮助将不胜感激。