read/write json from a map to a file. Why use a struct over a map? ... if you need to mix datatypes (hmm... dont... - use interface{}) you have to

jsonmap.go

package main

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

var stderr = log.New(os.Stderr, "RUHROH-->", 0)

func main() {

	// age 10 years :(
	var dataMap map[string]int = load("testmap.json")
	for i := 0; i < 10; i++ {
		dataMap["Age"] += 1
		save("testmap.json", dataMap)
	}
}

func load(filename string) map[string]int {
	dataMap := make(map[string]int)
	data, err := ioutil.ReadFile(filename)
	//	f, err := os.Open(filename)
	if err == nil {

		err = json.Unmarshal(data, &dataMap)

		if err != nil {
			stderr.Println("parsing config file", err.Error())
		}

	} else {
		stderr.Println("opening json file", err.Error())
	}

	return dataMap

}

func save(filename string, dataMap map[string]int) {

	json, err := json.Marshal(dataMap)
	if err == nil {
		err = ioutil.WriteFile(filename, []byte(json), 0644)
		if err != nil {
			stderr.Println(err)
		}
	} else {
		stderr.Println(err)
	}

}