You have now transformed the easy problem of "iterate through some files" into the much more complex problem of either finding a work queue library or writing your own work queue library; and you're baking in the assumption that the only reasonable way to use that work queue is to make each work item exactly one file.

What you propose is not a bad solution, but don't come here and pretend it's the only reasonable solution for almost all situations. It's not. Sometimes, you want each work item to be a list of files, if processing one file is fast enough for synchronisation overhead to be significant. Often, you don't have to care so much about the wall clock time your loop takes and it's fast enough to just do sequentially. Sometimes, you're implementing a non-important background task where you intentionally want to only bother one core. None of these are super unusual situations.

It is telling that you keep insisting that any solution that's not a one-file-per-work-item work queue is super strange and should be punished by the language's design, when you haven't even responded to my core argument that: sometimes sequential is fast enough.

Using a "work queue", i.e. a channel would still have a for loop like

  for filename := range workQueue {
      fp, err := os.Open(filename)
      if err != nil { ... }
      defer fp.Close()
      // do work
  }