concurrency: use channel to handle racing situation

concurrency/concurrency.go

@@ -1,17 +1,31 @@
 package concurrency
 
-import "time"
-
 type WebsiteChecker func(string) bool
 
+type result struct {
+	string
+	bool
+}
+
 func CheckWebsites(wc WebsiteChecker, urls []string) map[string]bool {
 	results := make(map[string]bool)
+	resultChannel := make(chan result)
 
 	for _, url := range urls {
 		go func(u string) {
-			results[u] = wc(u)
+			resultChannel <- result{u, wc(u)}
 		}(url)
 	}
-	time.Sleep(2 * time.Second)
+	// XXX: it seems that this works on Go 1.23
+	// for _, u := range urls {
+	// 	go func() {
+	// 		resultChannel <- result{u, wc(u)}
+	// 	}()
+	// }
+	for i := 0; i < len(urls); i++ {
+		r := <-resultChannel
+		results[r.string] = r.bool
+	}
+
 	return results
 }