Use Task.async in website.brokenRemoteLinks (#5814)

Pull request: #5814

Author: lefou

website/package.mill

@@ -526,17 +526,24 @@ object `package` extends mill.Module {
 
     // Try to fetch all the links serially. It isn't worth trying to parallelize it
     // because if we go too fast the remote websites tend to rate limit us anyway
-    val linksToStatusCodes = allLinks.toSeq.zipWithIndex
+    val linksToStatusCodesFut = allLinks.toSeq.zipWithIndex
       .map { case (link, i) =>
         val key = s"$i/${allLinks.size}"
-        println(s"Checking link $link $key")
-        val start = System.currentTimeMillis()
-        val res = requests.head(link, check = false).statusCode
-        val duration = System.currentTimeMillis() - start
-        val remaining = 1000 - duration
-        if (remaining > 0) Thread.sleep(remaining) // try to avoid being rate limited
-        (link, res)
+        Task.fork.async(
+          dest = Task.dest,
+          key = key,
+          message = s"Checking link $link"
+        ) { logger =>
+          val start = System.currentTimeMillis()
+          val res = requests.head(link, check = false).statusCode
+          val duration = System.currentTimeMillis() - start
+          val remaining = 1000 - duration
+          if (remaining > 0) Thread.sleep(remaining) // try to avoid being rate limited
+          (link, res)
+        }
       }
+
+    val linksToStatusCodes = Task.fork.awaitAll(linksToStatusCodesFut)
       .toMap
 
     allLinksAndAnchors()