Split slices s into all substrings separated by sep and returns a slice of the substrings between those separators.
If s does not contain sep and sep is not empty, Split returns a slice of length 1 whose only element is s.
If sep is empty, Split splits after each UTF-8 sequence. If both s and sep are empty, Split returns an empty slice.
It is equivalent to SplitN with a count of -1.