Chi

package main

import (
	"context"
	"crypto/subtle"
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"os"
	"strconv"
	"sync"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/go-chi/cors"
)

type User struct {
	ID    int    `json:"id"`
	Name  string `json:"name"`
	Email string `json:"email"`
}

type store struct {
	mu    sync.RWMutex
	users map[int]User
	next  int
}

func (s *store) find(id int) (User, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	u, ok := s.users[id]
	if !ok {
		return User{}, errors.New("not found")
	}
	return u, nil
}

func (s *store) add(u User) User {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.next++
	u.ID = s.next
	s.users[u.ID] = u
	return u
}

type ctxKey string

const userKey ctxKey = "user"

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(v)
}

func newRouter(db *store, apiKey string) http.Handler {
	r := chi.NewRouter()

	r.Use(middleware.RequestID)
	r.Use(middleware.ClientIPFromRemoteAddr) // direct exposure; behind a proxy pick another ClientIPFrom*
	r.Use(middleware.Logger)
	r.Use(middleware.Recoverer)
	r.Use(middleware.Timeout(30 * time.Second))
	r.Use(cors.Handler(cors.Options{
		AllowedOrigins: []string{"https://app.shopwave.io"},
		AllowedMethods: []string{"GET", "POST", "PUT", "DELETE"},
		AllowedHeaders: []string{"Authorization", "Content-Type"},
		MaxAge:         300,
	}))

	r.Get("/health", func(w http.ResponseWriter, r *http.Request) {
		writeJSON(w, http.StatusOK, map[string]string{"status": "ok", "client": middleware.GetClientIP(r.Context())})
	})

	r.Route("/api", func(r chi.Router) {
		r.Use(requireKey(apiKey))
		r.Route("/users", func(r chi.Router) {
			r.Post("/", func(w http.ResponseWriter, r *http.Request) {
				var in User
				if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<20)).Decode(&in); err != nil || in.Email == "" {
					writeJSON(w, http.StatusBadRequest, map[string]string{"error": "name and email are required"})
					return
				}
				writeJSON(w, http.StatusCreated, db.add(in))
			})
			r.Route("/{userID}", func(r chi.Router) {
				r.Use(userCtx(db))
				r.Get("/", func(w http.ResponseWriter, r *http.Request) {
					writeJSON(w, http.StatusOK, r.Context().Value(userKey).(User))
				})
			})
		})
	})
	return r
}

func requireKey(want string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			got := r.Header.Get("Authorization")
			if subtle.ConstantTimeCompare([]byte(got), []byte("Bearer "+want)) != 1 {
				writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "unauthorized"})
				return
			}
			next.ServeHTTP(w, r)
		})
	}
}

func userCtx(db *store) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			id, err := strconv.Atoi(chi.URLParam(r, "userID"))
			if err != nil {
				writeJSON(w, http.StatusBadRequest, map[string]string{"error": "bad id"})
				return
			}
			u, err := db.find(id)
			if err != nil {
				writeJSON(w, http.StatusNotFound, map[string]string{"error": "user not found"})
				return
			}
			next.ServeHTTP(w, r.WithContext(context.WithValue(r.Context(), userKey, u)))
		})
	}
}

func main() {
	key := os.Getenv("API_KEY")
	if key == "" {
		log.Fatal("API_KEY is not set")
	}
	db := &store{users: map[int]User{}}
	srv := &http.Server{
		Addr:              "127.0.0.1:3000",
		Handler:           newRouter(db, key),
		ReadHeaderTimeout: 5 * time.Second,
	}
	log.Fatal(srv.ListenAndServe())
}

$ API_KEY=shopwave-dev-key go run .
$ curl -s localhost:3000/health
{"client":"127.0.0.1","status":"ok"}
$ curl -s -X POST localhost:3000/api/users -H 'Authorization: Bearer shopwave-dev-key' -d '{"name":"Ada","email":"ada@shopwave.io"}'
{"id":1,"name":"Ada","email":"ada@shopwave.io"}
$ curl -s -o /dev/null -w '%{http_code}\n' localhost:3000/api/users/1
401

package main

import (
	"net/http/httptest"
	"strings"
	"testing"
)

func TestUsers(t *testing.T) {
	srv := newRouter(&store{users: map[int]User{}}, "shopwave-dev-key")
	do := func(method, path, body, auth string) *httptest.ResponseRecorder {
		req := httptest.NewRequest(method, path, strings.NewReader(body))
		req.Header.Set("Authorization", auth)
		rec := httptest.NewRecorder()
		srv.ServeHTTP(rec, req)
		return rec
	}
	if c := do("GET", "/api/users/1", "", "").Code; c != 401 {
		t.Fatalf("want 401, got %d", c)
	}
	auth := "Bearer shopwave-dev-key"
	if c := do("POST", "/api/users", `{"name":"Ada","email":"ada@shopwave.io"}`, auth).Code; c != 201 {
		t.Fatalf("want 201, got %d", c)
	}
	if c := do("GET", "/api/users/1", "", auth).Code; c != 200 {
		t.Fatalf("want 200, got %d", c)
	}
	if c := do("GET", "/api/users/9", "", auth).Code; c != 404 {
		t.Fatalf("want 404, got %d", c)
	}
}