golang parallelMap

parmap.go

func parallelMap[T any, V any](input []T, f func(T) (V, error)) ([]V, error) {
  outChan := make(chan V, len(input))
  errChan := make(chan error, len(input))

  for i, val := range input {
    go func(i int, val T) {
      out, err := f(val)
      if err != nil {
        errChan <- err
      } else {
        outChan <- out
      }
    }(i, val)
  }

  output := make([]V, len(input))

  for i := 0; i < len(input); i++ {
    select {
    case out := <-outChan:
      output[i] = out
    case err := <-errChan:
      return []V{}, err
    }
  }

  return output, nil
}