Data has
many dialects.

// main.go: a tiny Go API that speaks JSON
package main

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

// Task matches the TypeScript type field for field.
// The `json:"..."` tags set the key names in the JSON.
type Task struct {
	ID    int    `json:"id"`
	Title string `json:"title"`
	Done  bool   `json:"done"`
}

var (
	mu    sync.Mutex
	tasks = []Task{
		{ID: 1, Title: "Learn JSON", Done: true},
	}
)

func main() {
	// GET /tasks: Go data -> JSON text
	http.HandleFunc("GET /tasks", func(w http.ResponseWriter, r *http.Request) {
		mu.Lock()
		defer mu.Unlock()
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(tasks)
	})

	// POST /tasks: JSON text -> Go data
	http.HandleFunc("POST /tasks", func(w http.ResponseWriter, r *http.Request) {
		var t Task
		if err := json.NewDecoder(r.Body).Decode(&t); err != nil {
			http.Error(w, "bad JSON: "+err.Error(), http.StatusBadRequest)
			return
		}
		mu.Lock()
		t.ID = len(tasks) + 1
		tasks = append(tasks, t)
		mu.Unlock()
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusCreated)
		json.NewEncoder(w).Encode(t)
	})

	fmt.Println("listening on http://localhost:8080")
	log.Fatal(http.ListenAndServe("localhost:8080", nil))
}

// client.ts: TypeScript talking to the Go API with JSON

// The same shape as the Go struct
type Task = {
  id: number;
  title: string;
  done: boolean;
};

const API = "http://localhost:8080/tasks";

async function main(): Promise<void> {
  // Send: TypeScript data -> JSON text -> Go
  const res = await fetch(API, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ title: "Learn Go", done: false }),
  });
  if (!res.ok) throw new Error(await res.text());
  const created: Task = await res.json();
  console.log(`Go saved #${created.id}: ${created.title}`);

  // Receive: Go -> JSON text -> TypeScript data
  const tasks: Task[] = await (await fetch(API)).json();
  for (const t of tasks) {
    console.log(`  [${t.done ? "x" : " "}] #${t.id} ${t.title}`);
  }
}

main();