I have installed pgsodium into the database using CREATE EXTENSION pgsodium.
This is the output from dx

citext   | 1.6     | public  
pgsodium | 3.1.9   | pgsodium 
plpgsql  | 1.0     | pg_catalog

In PLSQL I can successfully do ..
SELECT pgsodium.crypto_pwhash_str('password');

However when I try to do the same in a trigger function I get the error

ERROR:  function pgsodium.crypto_pwhash_str(text) does not exist
LINE 1: SELECT pgsodium.crypto_pwhash_str(NEW.password)

This is the function

CREATE OR REPLACE FUNCTION update_user() RETURNS TRIGGER AS $update_user$
BEGIN
    SELECT pgsodium.crypto_pwhash_str(NEW.password) INTO NEW.password;
    RETURN NEW;
END
$update_user$ LANGUAGE plpgsql;

How do I execute the function inside the trigger?