code: func resolveGoModFile(dir string) (*os.File, string, error) {
  	goModPath := filepath.Join(dir, "go.mod")
  	f, err := os.Open(goModPath)
  	if err != nil {
  		if os.IsNotExist(err) && dir != filepath.Dir(dir) {
  			return resolveGoModFile(filepath.Dir(dir))
  		}
  		return nil, "", err
  	}
  	return f, dir, nil
  }
docs: // resolveGoModFile walks up the directory tree starting from 'dir' until it
  // finds a go.mod file. If go.mod is found it will return the related file
  // object. If no go.mod file is found it will return an error.