go options 模式

...

函数式选项模式的使用场景有哪些呢：我们一般用来配置一些基础的服务配置，比如MySQL，Redis，Kafka的配置，很多可选参数，可以方便动态灵活的配置想要配置的参数。

https://zhuanlan.zhihu.com/p/436468481

type Option func(*User)

func WithAge(age int) Option {
    return func(u *User) {
        u.Age = age
    }
}

func WithEmail(email string) Option {
    return func(u *User) {
        u.Email = email
    }
}

func WithPhone(phone string) Option {
    return func(u *User) {
        u.Phone = phone
    }
}

func WithGender(gender string) Option {
    return func(u *User) {
        u.Gender = gender
    }
}

func NewUser(id string, name string, options ...func(*User)) (*User, error) {
    user := User{
        ID:     id,
        Name:   name,
        Age:    0,
        Email:  "",
        Phone:  "",
        Gender: "female",
    }
    for _, option := range options {
        option(&user)
    }
    //...
    return &user, nil
}

user1, err := NewUser("1", "ada")
user2, err := NewUser("2", "bob", WithPhone("123456"), WithGender("male"))