Matches returns true if a string value matches a specific regexp pattern.

New is a helper which creates a new Validator instance with an empty errors map.

Generic function which returns true if a specific value is in a list.

TODO: Will have to make a string specific one such that it can compare strings STRINGS MUST BE lowercase BEFORE comparison.

Generic function which returns true if all values in a slice are unique.

Declare a regular expression for sanity checking the format of email addresses (we'll use this later in the book).

Define a new Validator type which contains a map of validation errors.