Comment by a-poor

This means you can't pass variables in as function arguments. Even the example in the official go docs doesn't handle the scope correctly:

  func main() {
   var wg sync.WaitGroup
   var urls = []string{
    "http://www.golang.org/",
    "http://www.google.com/",
    "http://www.example.com/",
   }
   for _, url := range urls {
    // Launch a goroutine to fetch the URL.
    wg.Go(func() {
     // Fetch the URL.
     http.Get(url)
    })
   }
   // Wait for all HTTP fetches to complete.
   wg.Wait()
  }

https://pkg.go.dev/sync#example-WaitGroup

You need to use this pattern instead:

   for _, url := range urls {
    url := url
    // ...