json

config.WithOptions(config.ParseEnv)

// add Decoder and Encoder
config.AddDriver(Driver)

err := config.LoadFiles("testdata/json_base.json")
if err != nil {
	panic(err)
}

fmt.Printf("config data: \n %#v\n", config.Data())

err = config.LoadFiles("testdata/json_other.json")
// config.LoadFiles("testdata/json_base.json", "testdata/json_other.json")
if err != nil {
	panic(err)
}

fmt.Printf("config data: \n %#v\n", config.Data())
fmt.Print("get config example:\n")

name, ok := config.String("name")
fmt.Printf("get string\n - ok: %v, val: %v\n", ok, name)

arr1, ok := config.Strings("arr1")
fmt.Printf("get array\n - ok: %v, val: %#v\n", ok, arr1)

val0, ok := config.String("arr1.0")
fmt.Printf("get sub-value by path 'arr.index'\n - ok: %v, val: %#v\n", ok, val0)

map1, ok := config.StringMap("map1")
fmt.Printf("get map\n - ok: %v, val: %#v\n", ok, map1)

val0, ok = config.String("map1.key")
fmt.Printf("get sub-value by path 'map.key'\n - ok: %v, val: %#v\n", ok, val0)

// can parse env name(ParseEnv: true)
fmt.Printf("get env 'envKey' val: %s\n", config.DefString("envKey", ""))
fmt.Printf("get env 'envKey1' val: %s\n", config.DefString("envKey1", ""))

// set value
config.Set("name", "new name")
name, ok = config.String("name")
fmt.Printf("set string\n - ok: %v, val: %v\n", ok, name)

// if you want export config data
// buf := new(bytes.Buffer)
// _, err = config.DumpTo(buf, config.JSON)
// if err != nil {
// 	panic(err)
// }
// fmt.Printf("export config:\n%s", buf.String())

Output: