将查询结果从结构转换为另一个Golang包的字符串

Question

I have searched for a solution on the net and in SO, but found nothing that apply to return values. It is a simple sql query with several rows that I want to return. Error handling not included:

func Fetch(query string) (string) {

    type User struct{
        id string
        name string
    }

    rows, err := db.Query(query)

    users := make([]*User, 0)
    for rows.Next() {
      user := new(User)
      err := rows.Scan(&user.id, &user.name)
      users = append(users, user)
    }

    return(users)
}

I get this error when compiling:

cannot use users (type []*User) as type string in return argument

How should I do to get a correct return value?

The expected input is

JD John Doe --OR-- {id:"JD",name:"John Doe"}

Answer 1

If you have to return a String you can use the encoding/json package to serialize your user object, but you have to use fields that begin with capital letters for them to be exported. See the full example:

import (
    "encoding/json"
)

func Fetch(query string) (string) {

    type User struct{
        Id string  // <-- CHANGED THIS LINE
        Name string // <-- CHANGED THIS LINE
    }

    rows, err := db.Query(query)

    users := make([]*User, 0)
    for rows.Next() {
      user := new(User)
      err := rows.Scan(&user.id, &user.name)
      users = append(users, user)
    }

    return(ToJSON(users)) // <-- CHANGED THIS LINE
}

func ToJSON(obj interface{}) (string) {
    res, err := json.Marshal(obj)
    if err != nil {
      panic("error with json serialization " + err.Error())
    }
    return string(res)
}