type User struct {
    id    int
    name  string
    age   int
    class string
}

// 官网例子
type ColorGroup struct {
    ID     int
    Name   string
    Colors []string
}

func (this *UserController) Get() {
    fmt.Println(this.Ctx.Input.Param(":user"))
    a, _ := this.GetInt(":user")
    fmt.Println("hello")
    fmt.Println(a)
    time.Sleep(time.Duration(a) * time.Second)
    //this.Ctx.WriteString("hello World")
    user := User{
        id:    1,
        name:  "wang",
        age:   22,
        class: "class1",
    }
    body, err := json.Marshal(user)
    if err != nil {
        fmt.Println("Error: ", err)
    }
    fmt.Println("user: ",string(body))
    group := ColorGroup{
        ID:     1,
        Name:   "Reds",
        Colors: []string{"Crimson", "Red", "Ruby", "Maroon"},
    }
    b, err := json.Marshal(group)
    if err != nil {
        fmt.Println("error:", err)
    }

    fmt.Println("color: ",string(b))
    this.Ctx.WriteString(string(body))
}

output

{}
{"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}

上面的user结构体序列化之后为 空 应该修改为：

type User struct {
    Id    int  // 首字母大写
    Name  string
    Age   int
    Class string
}

必须要field的首字母大写才能成功的解析为json格式的数据,或者tag(field首字母还是必须要大写,不然为 空 ).不然为空.