How to call pgx.Tx CopyFrom with sql.Tx

pgx.Tx supports CopyFrom but there seems to be no way to use it from sql driver. Raw call will only produce pgx.Conn object but I don't see a way to call CopyFrom via sql.Tx

Start by reading the pgx.Tx, pgx.Conn, and sql.Tx APIs and how the SQL driver exposes raw connections. Determine whether CopyFrom can be supported through sql.Tx or requires a new integration boundary; done means documenting the supported path or defining the required API change.

Written by the indexing model from the issue text.