✨ feat:concur test

Makefile

@@ -16,7 +16,7 @@ devrun=docker run $(devrunopts) --rm \
 ## run isolated tests
 .PHONY: test
 test:
-	go test ./... -timeout 10s -race -shuffle on
+	go test -run="$(testcase)" ./... -timeout 10s -race -shuffle on
 
 ## Run lint
 .PHONY: lint

metrica_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
+	"sync"
 	"testing"
 )
 
@@ -47,6 +48,28 @@ func TestHandlerCount_Multiple(t *testing.T) {
 	}
 }
 
+func TestHandlerCount_Concurrent(t *testing.T) {
+	c := NewAtomicCounter()
+	mux := Handler(c)
+	var wg sync.WaitGroup
+
+	for i := 0; i < 1000; i++ {
+		wg.Add(1)
+		go func() {
+			req := httptest.NewRequest("GET", "/count", nil)
+			w := httptest.NewRecorder()
+			mux.ServeHTTP(w, req)
+			if w.Code != http.StatusOK {
+				t.Errorf("expected status OK; got %v", w.Code)
+			}
+			defer wg.Done()
+		}()
+	}
+	wg.Wait()
+
+	assert(t, int64(1000), c.Value())
+}
+
 func assert(t *testing.T, want interface{}, got interface{}) {
 	if want != got {
 		t.Errorf("expected %v; got %v", want, got)