Table of Contents

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.

Examples

json.Unmarshal function can be used to convert a JSON to the map

There can be two cases

If you know the format of the JSON, then initialize the map in the same format. For eg when we know that the value part in the JSON is of string type then we can initialize the map in the below format

map[string]string

If the format of the JSON is not known then the corresponding map needs to be initialized in the below format. The value part needs to be an empty interface

map[string]interface{}

Let’s see some examples. In the first example, we have below JSON string

{"1":"John"}

Assume that the format of the JSON is known. Below is the program

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	j := `{"1":"John"}`
	var b map[string]string
	json.Unmarshal([]byte(j), &b)

	fmt.Println(b)
}

Output

map[1:John]

In the second example, we have below JSON string

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

We are parsing this JSON string into the below map type

map[int]employee

where the employee is a struct

type employee struct {
    Name string
}

This is the code

package main

import (
	"encoding/json"
	"fmt"
)

type employee struct {
	Name string
}

func main() {
	j := `{"1":{"Name":"John"}}`
	var b map[int]employee
	json.Unmarshal([]byte(j), &b)

	fmt.Println(b)
}

Output

map[1:{John}]

Let’s also see an example of the case where the format of the JSON is not known.

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	j := `{"1":"John"}`
	var b map[string]interface{}
	json.Unmarshal([]byte(j), &b)

	fmt.Println(b["1"])
}

Output

John

golang