Add support for pgx
Add support for pgx

beni55/sqlx,wmydz1/sqlx,adcaes/sqlx,johnsto/sqlx,jmoiron/sqlx,aiyi/sqlx,proteneer/sqlx,StabbyCutyou/sqlx,cortex/sqlx,outrightmental/go-sqlx,snikch/sqlx,larsth/sqlx