Please note that I've only used the standard library so far and therefore my assumption that an ORM will behave in the same manner as the
database/sql package might very well be wrong.
I believe any ORM that exposes an interface analogous to the standard one that allows you to execute plain sql statements, like xorm and gorm for example do, should be able to facilitate switching between schemas by setting the
db.Exec("SET search_path TO tenant_schema_123")
This sets the schema for the db handle and any successive queries using that db handle are made to