code: func findInDir(file, dir string, env environ.Env) (string, error) {
  	// NOTE(rsc): I wish we could use the Plan 9 behavior here
  	// (only bypass the path if file begins with / or ./ or ../)
  	// but that would not match all the Unix shells.
  
  	if dir == "" {
  		// Unix shell semantics: path element "" means "."
  		dir = "."
  	}
  	path := filepath.Join(dir, file)
  	if err := findExecutable(path); err == nil {
  		return path, nil
  	}
  	return "", errors.New("not found")
  }
docs: // findInDir is a paraphrased and trimmed version of "exec.LookPath"
  // (for Windows),
  //
  // Copied from:
  // https://github.com/golang/go/blob/d234f9a75413fdae7643e4be9471b4aeccf02478/src/os/exec/lp_unix.go
  //
  // Modified to:
  //	- Use a supplied "dir" instead of scanning through PATH.
  //	- Not consider cases where "file" is an absolute path
  //	- Ignore the possibility that "file" may be in the CWD; only look in "dir".