Overview

encoding/json package provides utilities that can be used to convert to and from JSON. The same utility can be used to convert a golang map to JSON string and vice versa. A very important point to note though is that map allows integer values for keys while JSON doesn’t allow integer values for keys. JSON only allows string value for keys. So a map having an integer value for the key when converted to JSON will have a string value for the key.

Example

Let’s see a program for conversion of the map to JSON

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	a := make(map[int]string)

	a[1] = "John"

	j, err := json.Marshal(a)
	if err != nil {
		fmt.Printf("Error: %s", err.Error())
	} else {
		fmt.Println(string(j))
	}
}

Output

{"1":"John"}

In the above code, we are using json.Marshal function to convert the map to JSON. The map has an integer value for the key.

a := make(map[int]string)

While after converting, the resultant JSON as a string value for the key

{"1":"John"}

Let’s see one more example where we convert a map to a JSON where we have a struct for the value in the map. Below is the code for that

package main
import (
    "encoding/json"
    "fmt"
)
type employee struct {
    Name string
}
func main() {
    a := make(map[string]employee)
    a["1"] = employee{Name: "John"}
    j, err := json.Marshal(a)
    if err != nil {
        fmt.Printf("Error: %s", err.Error())
    } else {
        fmt.Println(string(j))
    }
}

Output

{"1":{"Name":"John"}}