refactor: simplify checkout handler

internal/stripe/client.go

@@ -36,8 +36,8 @@ func (s *Service) CreateSession(ctx context.Context, req CheckoutSessionRequest)
 		quantity = 1
 	}
 
-    params := &stripe.CheckoutSessionParams{}
-    params.Context = ctx
+	params := &stripe.CheckoutSessionParams{}
+	params.Context = ctx
 	params.SuccessURL = stripe.String(s.product.SuccessURL)
 	params.CancelURL = stripe.String(s.product.CancelURL)
 	params.Mode = stripe.String(string(stripe.CheckoutSessionModePayment))

internal/web/handlers.go

@@ -10,16 +10,13 @@ import (
 )
 
 func (h *Handler) createCheckoutSession(w http.ResponseWriter, r *http.Request) {
-	if r.Method != http.MethodPost {
-		w.Header().Set("Allow", http.MethodPost)
-		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
-		return
-	}
-
-	defer r.Body.Close()
-
 	var req stripe.CheckoutSessionRequest
+
 	if r.Body != nil {
+		defer func(body io.ReadCloser) {
+			_ = body.Close()
+		}(r.Body)
+
 		dec := json.NewDecoder(r.Body)
 		dec.DisallowUnknownFields()
 
@@ -30,9 +27,7 @@ func (h *Handler) createCheckoutSession(w http.ResponseWriter, r *http.Request)
 				http.Error(w, "invalid request payload", http.StatusBadRequest)
 				return
 			}
-		}
-
-		if dec.More() {
+		} else if dec.More() {
 			http.Error(w, "unexpected data in request body", http.StatusBadRequest)
 			return
 		}

internal/web/handlers_test.go

@@ -110,11 +110,13 @@ func TestCreateCheckoutSessionStripeFailure(t *testing.T) {
 
 func TestCreateCheckoutSessionMethodNotAllowed(t *testing.T) {
 	handler := &Handler{checkout: &fakeCheckoutService{}}
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /api/checkout", handler.createCheckoutSession)
 
 	req := httptest.NewRequest(http.MethodGet, "/api/checkout", http.NoBody)
 	rec := httptest.NewRecorder()
 
-	handler.createCheckoutSession(rec, req)
+	mux.ServeHTTP(rec, req)
 
 	if rec.Code != http.StatusMethodNotAllowed {
 		t.Fatalf("expected status 405, got %d", rec.Code)

internal/web/server.go

@@ -25,7 +25,7 @@ func NewServer(cfg config.Config) http.Handler {
 	h := &Handler{cfg: cfg, checkout: checkoutSvc}
 
 	mux := http.NewServeMux()
-	mux.HandleFunc("/api/checkout", h.createCheckoutSession)
+	mux.HandleFunc("POST /api/checkout", h.createCheckoutSession)
 
 	return mux
 }