CutLast is [strings.Cut], but cutting at the last occurrence of sep rather than the first.

CutPrefix behaves like strings.Cut, but only cuts a prefix, not anywhere in the string.

CutSuffix behaves like strings.Cut, but only cuts a suffix, not anywhere in the string.

CutTwice calls strings.Cut twice to split s into three strings.

ReadJSONFile reads one JSON value from the specified file.

WriteJSONFile writes one specified value to a file as indented JSON with a trailing newline.