func Pattern(filename string) string
Pattern returns a glob pattern that matches the unrenamed temporary files created when writing to filename.
func WriteFile(filename string, data []byte) (err error)
WriteFile is like ioutil.WriteFile, but first writes data to an arbitrary file in the same directory as filename, then renames it atomically to the final name.
That ensures that the final location, if it exists, is always a complete file.
func WriteToFile(filename string, data io.Reader) (err error)
WriteToFile is a variant of WriteFile that accepts the data as an io.Reader instead of a slice.