Worse versions of packages that already exist.
Just the consts.
Package flag provides a very minimal command line flag parser. Both short flags (-s) and long flags (--long) are supported. Short flags can be chained (-xvzf) and "--" is treated as the end of flags marker. Boolean and integer values have first-class support; strings values are intended to serve as a catch-all for anything else.
Package gitignore can be used to parse .gitignore-style files into globs that can be used to test against a certain string or selectively walk a file tree. Gobwas's glob package is used for matching because it is faster than using regexp, which is overkill, and supports globstars (**), unlike filepath.Match.
Package replaceright provides similar functionality to some of the standard library string replacement routines except they start from the right. Uses Boyer-Moore on longer strings.