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This article describes how to convert JSON to struct in GoLang .

Convert JSON to Struct using Unmarshal method in Go

The encoding/json package of the Go language provides a function Unmarshalto convert JSON data into byte format. This function can parse structured and unstructured JSON data into a byte []byteformat.

We can use this byte conversion to convert JSON to a struct. Let's try an example of converting JSON to a struct using the Unmarshal method:

package main

import (
    "encoding/json"
    "fmt"
)

type Employee struct {
    Name     string
    ID       int
    Salary   int
    Position string
}

func main() {
    EmployeeJSON := `{"Name": "Sheeraz", "ID": 10, "Salary": 3000, "Position": "Senior Developer" }`

    var employees Employee

    json.Unmarshal([]byte(EmployeeJSON), &employees)

    fmt.Printf("Name: %s, ID: %d , Salary: %d , Position: %s", employees.Name, employees.ID, employees.Salary, employees.Position)

    fmt.Println("\n", employees)
}

The above code uses the Unmarshal method of GoLang's JSON standard library to convert the given JSON into a structure. See the output:

Name: Sheeraz, ID: 10 , Salary: 3000 , Position: Senior Developer

{Sheeraz 10 3000 Senior Developer}

Convert JSON array to struct in Go

As we can see, the above example converts a single JSON to a struct, but what if we have an array of JSON? Let's try an example that converts a JSON array to a struct:

package main

import (
    "encoding/json"
    "fmt"
)

type Employee struct {
    Name     string
    ID       int
    Salary   int
    Position string
}

func main() {
    EmployeeJSON := `[{"Name": "Sheeraz", "ID": 10, "Salary": 3000, "Position": "Senior Developer" },
    {"Name": "Jack", "ID": 20, "Salary": 2000, "Position": "Junior Developer" },
    {"Name": "John", "ID": 30, "Salary": 1500, "Position": "Junior Developer" },
    {"Name": "Mike", "ID": 40, "Salary": 1000, "Position": "Intern" }
    ]`

    var employees []Employee

    json.Unmarshal([]byte(EmployeeJSON), &employees)

    fmt.Printf("Employees Structs : %+v", employees)
}

The above code will convert the JSON array into a structure array. See the output:

Employees Structs : [
{Name:Sheeraz ID:10 Salary:3000 Position:Senior Developer}
{Name:Jack ID:20 Salary:2000 Position:Junior Developer}
{Name:John ID:30 Salary:1500 Position:Junior Developer}
{Name:Mike ID:40 Salary:1000 Position:Intern}]
Program exited.

Convert nested JSON to struct in Go

JSON is also created in nested form where one field in JSON contains another field. To convert this type of JSONS we have to create nested structure.

Let’s look at an example:

package main

import (
    "encoding/json"
    "fmt"
)

type EmployeeType struct {
    Gender   string
    Contract string
}

type Employee struct {
    Name         string
    ID           int
    Salary       int
    Position     string
    EmployeeType EmployeeType
}

func main() {
    EmployeeJSON := `{"Name": "Sheeraz", "ID": 10, "Salary": 3000, "Position": "Senior Developer", "EmployeeType": {"Gender": "Male" ,"Contract": "Fulltime"}  }`

    var employees Employee

    json.Unmarshal([]byte(EmployeeJSON), &employees)

    fmt.Printf("Name: %s, ID: %d , Salary: %d , Position: %s, Gender: %s, Contract: %s",
        employees.Name, employees.ID, employees.Salary, employees.Position, employees.EmployeeType.Gender, employees.EmployeeType.Contract)

    fmt.Println("\n", employees)
}

The above code will convert the nested JSON object into a nested structure. See the output:

Name: Sheeraz, ID: 10 , Salary: 3000 , Position: Senior Developer, Gender: Male, Contract: Fulltime
{Sheeraz 10 3000 Senior Developer {Male Fulltime}}

Program exited.