How to change Postgresql query according to the request in Golang?

Let's say I have this query and I'm using Golang to communicate

SELECT
    u."id",
    u."name",
    u.accreditation 
FROM
    universities u 
WHERE
    u.accreditation ILIKE ANY ( $1 ) 
    OR NOT u.accreditation ILIKE ANY ( '{A, B, C}' ) ;

The case is I want to make the query OR NOT u.accreditation ILIKE ANY ( '{A, B, C}' ) as a variable $2 like this

SELECT
    u."id",
    u."name",
    u.accreditation 
FROM
    universities u 
WHERE
    u.accreditation ILIKE ANY ( $1 ) 
    $2 ;

• If $1 contains "O" then $2 is OR NOT u.accreditation ILIKE ANY ( '{A, B, C}' ).
• If $1 does not contains "O" then $2 is <= empty string.

But it can't be done. What should I do?