正确从Golang输出JSON块

Question

I have search for a solution for this problem. It is actually from a sql database, but this illustrates the problem as well:

package main

import (
    "fmt"
    "encoding/json"
)

func main() {
    m := map[string]string{
      "USER_ID":"JD", 
      "USER_NAME":"John Doe",
    }

    json, _ := json.Marshal(m)
    for i := 0; i < 4; i++ {
       fmt.Println(string(json))
    }

}

https://play.golang.org/p/7DQPiB0aWAK

Each row is correct, but it each row is not separated by comma and surrounded by square brackets.

{"USER_ID":"JD","USER_NAME":"John Doe"}
{"USER_ID":"JD","USER_NAME":"John Doe"}
{"USER_ID":"JD","USER_NAME":"John Doe"}
{"USER_ID":"JD","USER_NAME":"John Doe"}

The desired output is this:

[{"USER_ID":"JD","USER_NAME":"John Doe"},
{"USER_ID":"JD","USER_NAME":"John Doe"},
{"USER_ID":"JD","USER_NAME":"John Doe"},
{"USER_ID":"JD","USER_NAME":"John Doe"}]

Is this possible using map[string]string or interface?

Answer 1

Is this possible using map[string]string or interface?

The answer is simple - You can use a slice whenever you want to produce a list output in JSON.

Here is your example with the desired output (playground) :

package main

import (
    "fmt"
    "encoding/json"
)

func main() {
    // define a slice of maps
    var mySlice []map[string]string

    // define a map
    m := map[string]string{
      "USER_ID":"JD", 
      "USER_NAME":"John Doe",
    }

    // add the map 4 times to the slice
    for i := 0; i < 4; i++ {
        mySlice = append(mySlice, m)
    }

    // print the slice
    json, _ := json.Marshal(mySlice)
    fmt.Println(string(json))
}
// Output: [{"USER_ID":"JD","USER_NAME":"John Doe"},{"USER_ID":"JD","USER_NAME":"John Doe"},{"USER_ID":"JD","USER_NAME":"John Doe"},{"USER_ID":"JD","USER_NAME":"John Doe"}]