How to parse JSON files in Golang?

Suppose we want to read a JSON file in Go. By reading, we mean that we want to convert the file data into a struct in Go.

Consider the JSON file shown below that we will use to read and then convert the data into the structure.

{
   "users": [
      {
         "name": "Mukul Latiyan",
         "social": {
            "facebook": "https://facebook.com/immukul",
            "twitter": "https://twitter.com/immukul",
            "linkedin": "https://linkedin.com/immukul"
         }
      },
      {
         "name": "Mayank",
         "social": {
            "facebook": "https://facebook.com/mayank101",
            "twitter": "https://twitter.com/mayank101",
            "linkedin": "https://linkedin.com/mayank101"
         }
      },
      {
         "name": "Deepak",
         "social": {
            "facebook": "https://facebook.com/deepak1",
            "twitter": "https://twitter.com/deepak1",
            "linkedin": "https://linkedin.com/deepak1"
         }
      }
   ]
}

The above JSON file should be saved by the name users.json. It contains different users and each user has a name and different social fields.

A very naive approach to read the above JSON in Golang is to make use of the unstructured approach. In the unstructured approach, we use the interfaces{} to read the JSON data.

Consider the code shown below that will allow us to read the users.json file.

Example 1

package main
import (
   "encoding/json"
   "fmt"
   "io/ioutil"
   "log"
   "os"
)

func main() {
   fileContent, err := os.Open("users.json")

   if err != nil {
      log.Fatal(err)
      return
   }

   fmt.Println("The File is opened successfully...")

   defer fileContent.Close()

   byteResult, _ := ioutil.ReadAll(fileContent)

   var res map[string]interface{}
   json.Unmarshal([]byte(byteResult), &res)

   fmt.Println(res["users"])
}

Output

If we run the command go run main.go on the above code, then we will get the following output in the terminal.

The File is opened successfully...

[map[name:Mukul Latiyan
social:map[facebook:https://facebook.com/immukul
linkedin:https://linkedin.com/immukul
twitter:https://twitter.com/immukul]] map[name:Mayank
social:map[facebook:https://facebook.com/mayank101
linkedin:https://linkedin.com/mayank101
twitter:https://twitter.com/mayank101]] map[name:Deepak
social:map[facebook:https://facebook.com/deepak1
linkedin:https://linkedin.com/deepak1
twitter:https://twitter.com/deepak1]]]

The next step is to create structs that will hold the JSON data. Consider the structs mentioned below.

type Users struct {
   Users []User `json:"users"`
}
type User struct {
   Name string `json:"name"`
   Social Social `json:"social"`
}

type Social struct {
   Facebook string `json:"facebook"`
   Twitter string `json:"twitter"`
   LinkedIn string `json:"linkedin"`
}

The final step is to make use of the json.Unmarshal() function.

Example 2

package main

import (
   "encoding/json"
   "fmt"
   "io/ioutil"
   "log"
   "os"
)

type Users struct {
   Users []User `json:"users"`
}

type User struct {
   Name string `json:"name"`
   Social Social `json:"social"`
}

type Social struct {
   Facebook string `json:"facebook"`
   Twitter string `json:"twitter"`
   LinkedIn string `json:"linkedin"`
}

func main() {
   fileContent, err := os.Open("users.json")

   if err != nil {
      log.Fatal(err)
      return
   }

   fmt.Println("The File is opened successfully...")

   defer fileContent.Close()

   byteResult, _ := ioutil.ReadAll(fileContent)

   var users Users

   json.Unmarshal(byteResult, &users)

   for i := 0; i < len(users.Users); i++ {
      fmt.Println("User Name: " + users.Users[i].Name)
      fmt.Println("Facebook Url: " + users.Users[i].Social.LinkedIn)
   }
}

Output

If we run the command go run main.go on the above code, then we will get the following output in the terminal.

The File is opened successfully...
User Name: Mukul Latiyan
Facebook Url: https://linkedin.com/immukul;
User Name: Mayank
Facebook Url: https://linkedin.com/mayank101
User Name: Deepak
Facebook Url: https://linkedin.com/deepak1