Convert map to JSON in Golang? [4 Methods]

Different methods in golang to convert map to JSON

In golang there are couple of methods using which we can easily convert map to JSON, some of the methods are:

1. Using json.Marshal() function
2. Using json.MarshalIndent() function
3. Using json.NewEncoder() function
4. Using jsoniter package

---

Method-1: Using json.Marshal() function

Here is an example where we are using json.Marshal() function to convert the map1 to a JSON encoded byte slice. The returned byte slice is later converted to a string.

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    // create a map
    map1 := map[string]int{
        "one":   1,
        "two":   2,
        "three": 3,
    }

    // convert the map to a JSON encoded byte slice
    jsonContent, err := json.Marshal(map1)
    if err != nil {
        fmt.Println(err)
        return
    }

    // convert the byte slice to a string
    jsonString := string(jsonContent)

    fmt.Println(jsonString) // {"one":1,"three":3,"two":2}
}

---

Method-2: Using json.NewEncoder() function

Another way to convert golang map to JSON is using json.Encoder() function. This function creates a new encoder that writes to an io.Writer interface. By passing an bytes.Buffer as the io.Writer implementation.

Here’s an example of how to use the json.NewEncoder function to convert a Go map to a JSON string:

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
)

func main() {
    // create a map
    map1 := map[string]int{
        "one":   1,
        "two":   2,
        "three": 3,
    }

    // create a new buffer
    var buf bytes.Buffer

    // create a new encoder that writes to the buffer
    encoder := json.NewEncoder(&buf)

    // encode the map to the buffer
    err := encoder.Encode(map1)
    if err != nil {
        panic(err)
    }

    // convert the buffer to a string
    jsonString := buf.String()

    fmt.Println(jsonString) // {"one":1,"two":2,"three":3}
}

Here we can configure the encoder to use a specific indentation or to sort the keys of the json object, by using the SetIndent and SetEscapeHTML methods of the encoder.

---

Method-3: Using json.MarshalIndent() function

This method is similar to the json.Marshal() function, but it formats the JSON output with indentation for better readability.

Here’s an example of how to use the json.MarshalIndent() function to convert a map to JSON in Go:

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    // Define the map
    map1 := map[string]interface{}{
        "name": "Some User",
        "age":  35,
        "address": map[string]string{
            "street": "Random St",
            "city":   "Some town",
            "state":  "Some state",
            "zip":    "12345",
        },
    }

    // Convert the map to JSON
    jsonContent, err := json.MarshalIndent(map1, "", "    ")
    if err != nil {
        fmt.Println(err)
        return
    }

    // Print the JSON data
    fmt.Println(string(jsonContent))
}

In the output you can see that the JSON is having proper indentation:

# go run main.go 
{
    "address": {
        "city": "Some town",
        "state": "Some state",
        "street": "Random St",
        "zip": "12345"
    },
    "age": 35,
    "name": "Some User"
}

---

Method-4: Using jsoniter package

Another way to convert gplang map to JSON is using jsoniter.Marshal() function part jsoniter package from github .

You have to install the package using

go get "github.com/json-iterator/go"

Sample Example:

package main

import (
    "fmt"

    jsoniter "github.com/json-iterator/go"
)

func main() {
    // create a map
    map1 := map[string]int{
        "one":   1,
        "two":   2,
        "three": 3,
    }

    // convert the map to a JSON encoded byte slice
    jsonContent, err := jsoniter.Marshal(map1)
    if err != nil {
        fmt.Println(err)
        return
    }

    // convert the byte slice to a string
    jsonString := string(jsonContent)

    fmt.Println(jsonString)
    // Output: {"one":1,"two":2,"three":3}
}

---

Summary

In this tutorial we covered various methods in golang to convert map to JSON using built-in and third party libraries. There are many other libraries which can also be used such as easyjson which we have not covered in this tutorial because of the complexity involved in creating the struct for the JSON.

You can try the examples and let us know if you face any issues.

---

References

Convert Go map to json - Stack Overflow