Convert map[string]interface{} to Struct as Generic Function in Go

 Posted on 2 August 2025  |  3 minutes  |  530 words  |  Duken Marga

Several Methods to Convert

There are several methods to convert map[string]interface{} to a struct in Go.

  • Using reflect. This is the fastest. But, it will produce complicated long code. If not well coded, it will have problems with nested map. I will not discuss this method.
  • Using json standard library. First we marshal the map as json string and after that unmarshal it as a struct. This is what I will be talking about. It is slow, but reliable. Nested map are handled performantly.
  • Using external library such as mitchellh/mapstructure. It is not maintained anymore. But, you can still use it, since it is stable and has achieved its original intention.
  • Using simple loop and check one by one using switch-case. You need to hard-coded all the map properties, hence it’s not practical since it can’t be reused for different struct type.

Converting to Struct

The code below is the original non-generic method that can be used to convert any map to string. Don’t forget to include the json tag as per your intention, so the json library can convert it correctly.

Try it on Go Playground: https://go.dev/play/p/gSKSk_t16MI

package main

import (
	"encoding/json"
	"fmt"
)


type Profile struct {
	Name struct {
		First string `json:"first"`
		Last string  `json:"last"`
	} `json:"name"`
	PhoneNumber string   `json:"phoneNumber"`
	Status      string   `json:"status"`
	Emails      []string `json:"emails"`	
}

func main() {
	mapping := map[string]any{
		"name": map[string]string{
			"first": "Duken",
			"last": "Marga",
		},
		"phoneNumber": "08000000000",
		"status": "active",
		"emails": []string{
			"myemail@gmail.com",
			"my2ndemail@gmail.com",
		},
	}

	// Marshal the map to a JSON byte slice
	jsonBytes, err := json.Marshal(mapping)
	if err != nil {
		fmt.Printf("json.Marshal: %v", err)
	}

	// Inspecting json
	fmt.Printf("jsonBytes: %+v\n", string(jsonBytes))

	// Unmarshal the JSON byte slice into the struct
	var myStruct Profile
	err = json.Unmarshal(jsonBytes, &myStruct)
	if err != nil {
		fmt.Printf("json.Unmarshal: %v", err)
	}

	fmt.Printf("Struct: %+v\n", myStruct)
}

Output:
jsonBytes: {"emails":["myemail@gmail.com","my2ndemail@gmail.com"],"name":{"first":"Duken","last":"Marga"},"phoneNumber":"08000000000","status":"active"}
Struct: {Name:{First:Duken Last:Marga} PhoneNumber:08000000000 Status:active Emails:[myemail@gmail.com my2ndemail@gmail.com]}

Generic Function

But, what if you need to reuse this code into a function that can handle any struct type? We can utilize generic in Go. This is a modified version using generic function. Original map is not necessarily map[string]any, but it literally can use map[any]any. But, the former is more common.

Try on Go Playground: https://go.dev/play/p/_qnY0HqLABO

package main

import (
	"encoding/json"
	"fmt"
)

type Profile struct {
	Name struct {
		First string `json:"first"`
		Last  string `json:"last"`
	} `json:"name"`
	PhoneNumber string   `json:"phoneNumber"`
	Status      string   `json:"status"`
	Emails      []string `json:"emails"`
}

func main() {
	mapping := map[string]any{
		"name": map[string]string{
			"first": "Duken",
			"last":  "Marga",
		},
		"phoneNumber": "08000000000",
		"status":      "active",
		"emails": []string{
			"myemail@gmail.com",
			"my2ndemail@gmail.com",
		},
	}

	// Profile is passed as the type
	// Now myStruct type is Profile
	myStruct, err := ConvertTo[Profile](mapping)
	if err != nil {
		fmt.Printf("Error converting to struct: %v", err)
	}

	fmt.Printf("Struct: %+v\n", myStruct)
}

// Generic function to convert map to any struct
func ConvertTo[T any](mapping map[string]any) (T, error) {
	var myStruct T

	// Marshal the map to a JSON byte slice
	jsonBytes, err := json.Marshal(mapping)
	if err != nil {
		fmt.Printf("json.Marshal: %v", err)
	}

	// Unmarshal the JSON byte slice into the struct
	err = json.Unmarshal(jsonBytes, &myStruct)
	if err != nil {
		fmt.Printf("json.Unmarshal: %v", err)
	}

	return myStruct, nil
}

Output:
Struct: {Name:{First:Duken Last:Marga} PhoneNumber:08000000000 Status:active Emails:[myemail@gmail.com my2ndemail@gmail.com]}
go 

See also