config.go

package main

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

type Config map[string]interface{}

func (c Config) Name() string {
	return c["name"].(string)
}

func (c Config) SecondNestedValue() bool {
	nested := c["nested"].([]interface{})
	second := nested[1].(map[string]interface{})
	value := second["value"].(bool)
	return value
}

func LoadConfig(path string) (Config, error) {
	var m Config
	data, err := ioutil.ReadFile(path)
	if err != nil {
		return m, err
	}

	err = json.Unmarshal(data, &m)
	return m, err
}

func main() {
	config, err := LoadConfig("config.json")
	if err != nil {
		panic(err)
	}

	fmt.Println("Config: ", config)
	fmt.Println("Name: ", config.Name())
	fmt.Println("SecondNestedValue ", config.SecondNestedValue())
}

config.json

{
    "name": "Jurek",
    "surname": "Ogórek",
    "nested": [{
        "value": true,
        "value2": 11
    },
    {
        "value": false ,
        "value2": 1
    }]
}