return nil, err
			}
			readers = append(readers, dirReaders...)
		} else {
			if !isValidFile(f) {
				fmt.Fprintf(cmd.ErrOrStderr(), "Skipping file %v, recognized file extensions are: %v\n", f, fileExtensions)
				continue
			}
			rs, err := gatherFile(f)
			if err != nil {
				return nil, err
			}
			readers = append(readers, rs)
		}
	}
	return readers, nil
}