add promise queue

1-js/11-async/07-async-await/01-rewrite-async-2/solution.md

@@ -0,0 +1,49 @@
+
+There are no tricks here. Just replace `.catch` with `try...catch` inside `demoGithubUser` and add `async/await` where needed:
+
+```js run
+class HttpError extends Error {
+  constructor(response) {
+    super(`${response.status} for ${response.url}`);
+    this.name = 'HttpError';
+    this.response = response;
+  }
+}
+
+async function loadJson(url) {
+  let response = await fetch(url);
+  if (response.status == 200) {
+    return response.json();
+  } else {
+    throw new HttpError(response);
+  }
+}
+
+// Ask for a user name until github returns a valid user
+async function demoGithubUser() {
+
+  let user;
+  while(true) {
+    let name = prompt("Enter a name?", "iliakan");
+
+    try {
+      user = await loadJson(`https://api.github.com/users/${name}`);
+      break; // no error, exit loop
+    } catch(err) {
+      if (err instanceof HttpError && err.response.status == 404) {
+        // loop continues after the alert
+        alert("No such user, please reenter.");
+      } else {
+        // unknown error, rethrow
+        throw err;
+      }
+    }      
+  }
+
+
+  alert(`Full name: ${user.name}.`);
+  return user;
+}
+
+demoGithubUser();
+```