[feature req] session startup query

[bjeanes]

Upon a new session/connection it is sometimes useful to run a query or two, such as:

SET statement_timeout = '2s';

or

SET plv8.start_proc = 'plv8_init';

In a situation where you are using a Pool connections might idle out or be refreshed, so I think this would have to be something that sqlx would provide a feature for (or some kind of "new connection" hook/closure) in order to be reliable.

I know this is pretty niche and probably not likely to be a high priority, but what do you think?

[abonander]

This is being discussed in #263.