Go でネストされた構造体を効率的に初期化するにはどうすればよいですか?

type domain struct {
    id string
}

type user struct {
    name     string
    domain   domain
    password string
}

type password struct {
    user user
}

type identity struct {
    methods  []string
    password password
}

type auth struct {
    identity identity
}

type tokenRequest struct {
    auth auth
}

func main() {
    req := &tokenRequest{
        auth: auth{
            identity: identity{
                methods: []string{"password"},
                password: password{
                    user: user{
                        name: os.Username,
                        domain: domain{
                            id: "default",
                        },
                        password: os.Password,
                    },
                },
            },
        },
    }

    fmt.Printf("%+v\n", req)
}