Generate a hashmap from a struct (without reflection magic), and then merge it with another map and return a merged json.

map_n_merge.go

/* The last I checked, this gist can be run at:
http://play.golang.org/p/5keNQZLqfR
*/

package main

import (
	"fmt"
	"encoding/json"
)

type This struct {
	a int
	b string
}

func (t This) getMap() *map[string]interface{} {
	return &map[string]interface{} {
		"a": t.a,
		"b": t.b,
	}
}

func (t This) merge(extra *map[string]interface{}) ([]byte, error) {
	this := *t.getMap()
	for i := range *extra {
		this[i] = (*extra)[i]
	}
	return json.Marshal(this)
}

func main() {
	t := This{1, "@"}
	merged, _ := t.merge(&map[string]interface {}{"c": "blah"})
	fmt.Println(string(merged))
}

/* Prints:
{"a":1,"b":"@","c":"blah"}
*/