Take a json request and output json with the same data but different keys.

translate_json.go

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
)

type Greetings struct {
	Greetings []Greeting `json:"data"`
}

type Greeting struct {
	From     string `json:"from"`
	To       string `json:"to"`
	Greeting string `json:"greeting"`
}

type RelationShip struct {
	Messages []Message `json:"data"`
}

type Message struct {
	From    string `json:"from"`
	To      string `json:"to"`
	Message string `json:"message"`
}

func main() {
	http.HandleFunc("/", Greet)
	http.ListenAndServe(":3000", nil)
}

func Greet(rw http.ResponseWriter, request *http.Request) {
	decoder := json.NewDecoder(request.Body)
	var greetings Greetings
	err := decoder.Decode(&greetings)
	if err != nil {
		panic(err)
	}

	for _, g := range greetings.Greetings {
		fmt.Printf("%s, to %s from %s.\n", g.Greeting, g.To, g.From)
	}

	var relationShip RelationShip
	for _, g := range greetings.Greetings {
		relationShip.Messages = append(
			relationShip.Messages, Message{
				To: g.To, From: g.From, Message: g.Greeting,
			},
		)
	}
	r, err := json.Marshal(&relationShip)
	if err != nil {
		panic(err)
	}
	fmt.Fprintln(rw, string(r))
}

example request

curl -d '{"data": [{"to":"drew","from":"jo","greeting":"Hey"},{"to":"lori", "from":"yuri","greeting":"what up?"}]}' http://localhost:3000