Go: Example of WaitGroup

var wg sync.WaitGroup
for i, file := range dir {
  wg.Add(1)
  go func(i int, file os.DirEntry) {
    defer wg.Done()
    fileEntropies, err := readFile(fileName + "/" + file.Name())
    if err != nil {
      panic(err)
    }
    entropiies[i] = fileEntropies
  }(i, file)
}

wg.Wait()