Comment by simiones

The `os` package, that is the main way everyone I've seen opens and reads files in Go, doesn't specify any restriction on its path syntax (except that it uses `string`, of course). I've tried using it on Linux with a file name that would be invalid UTF-8 and it works without any issues.

I for one hadn't even heard of the io/fs package that has the problems that you mention, and I don't remember ever seeing it used in an example. I've looked in a code base I help maintain, and the only uses I could find are related to some function type definitions that are used by filepath.WalkDir and filepath.Walk - and those functions explicitly document the fact that they don't use `io/fs` style paths when calling these functions - they don't even respect the path separator format:

  // WalkDir calls fn with paths that use the separator character appropriate
  // for the operating system. This is unlike [io/fs.WalkDir], which always
  // uses slash separated paths.
  func WalkDir(root string, fn fs.WalkDirFunc) error {

Where fs.WalkDirFunc is defined like this:

  type WalkDirFunc func(path string, d DirEntry, err error) error