goArgonPass is a Argon2 Password utility package for Go using the crypto library package Argon2 designed to be compatible with Passlib for Python and Argon2 PHP. Argon2 was the winner of the most recent Password Hashing Competition. This is designed for use anywhere password hashing and verification might be needed and is intended to replace implementations using bcrypt or Scrypt.
Add type checking around the Function parameter by creating an ArgonVariant type alias and two constants that contain valid values.
Leaving this as a raw string makes the package harder to use, and invites invalid values.