doc: update usage

README.md

@@ -5,12 +5,21 @@
 ## Usage
 
 ``` ts
-import { parseCookies, stringifyCookies } from "jsemaphore";
-cookies = "test=value; name=jsemaphore";
-let cookiesMap = parseCookies(cookies);
-cookiesMap.set("test", "new_value");
-const cookiesString = stringifyCookies(cookiesMap);
+// Simulate tasks that take 1 second
+async function task(s: Semaphore) {
+  await new Promise((resolve) => setTimeout(() => resolve(null), 1000));
+  s.release();
+}
+// Concurrency = 10
+const s = new Semaphore(10);
 
-// jest
-expect(cookiesString).toBe("test=new_value; name=jsemaphore");
+const tasks = new Array<Promise<void>>();
+
+// For total 40 tasks
+for (let i = 0; i < 40; i++) {
+  await s.acquire();
+  tasks.push(task(s));
+}
+
+await Promise.all(tasks); // The total cost time is about 4 seconds
 ```