refactor(concurrency): replaced manual WaitGroup management with new wg.Go() and removed redundant code.

cmd/main.go

@@ -23,11 +23,9 @@ import (
 func parallel(fns ...func()) {
 	var wg sync.WaitGroup
 	for _, fn := range fns {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
+		wg.Go(func() {
 			fn()
-		}()
+		})
 	}
 	wg.Wait()
 }