Meydan okuma 2 - HTTP servis

package main

import (
    "encoding/json"
    "fmt"
    "net/http"
    "net/http/httptest"
    "strings"
    "sync"
)

type Not struct {
    ID    int    `json:"id"`
    Metin string `json:"metin"`
}

type Depo struct {
    mu     sync.Mutex
    notlar []Not
    sonID  int
}

func main() {
    d := &Depo{notlar: []Not{}}
    mux := http.NewServeMux()
    mux.HandleFunc("POST /notlar", func(w http.ResponseWriter, r *http.Request) {
        var n Not
        if err := json.NewDecoder(r.Body).Decode(&n); err != nil || n.Metin == "" {
            http.Error(w, "geçersiz not", http.StatusBadRequest)
            return
        }
        d.mu.Lock()
        d.sonID++
        n.ID = d.sonID
        d.notlar = append(d.notlar, n)
        d.mu.Unlock()
        w.Header().Set("Content-Type", "application/json")
        w.WriteHeader(http.StatusCreated)
        json.NewEncoder(w).Encode(n)
    })
    mux.HandleFunc("GET /notlar", func(w http.ResponseWriter, r *http.Request) {
        d.mu.Lock()
        defer d.mu.Unlock()
        w.Header().Set("Content-Type", "application/json")
        json.NewEncoder(w).Encode(d.notlar)
    })

    mux.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest("POST", "/notlar", strings.NewReader(`{"metin":"süt al"}`)))
    rec := httptest.NewRecorder()
    mux.ServeHTTP(rec, httptest.NewRequest("GET", "/notlar", nil))
    fmt.Print(rec.Body.String())
}