Authenticate Nginx to Postgres with sslmode enabled

Is it possible to do this? An sslmode parameter doesn't exist. I was able to find some commentary below on the topic but "adding params" to the postgres_server directive as @PiotrSikora recommends doesn't seem possible.

• use SSL certificates to authenticate Nginx to Postgres

• verify that the Postgres instance I'm connecting to presents itself with a correct SSL certificate

You can do that by adding params to postgres_server.

Originally posted by @PiotrSikora in #10 (comment)

In fact, sslmode is explicitly hardcoded as disabled:

ngx_postgres/src/ngx_postgres_upstream.c

Lines 338 to 353 in 7950a25

	+ sizeof("sslmode=disable");
	connstring = ngx_pnalloc(pgdt->request->pool, len);
	if (connstring == NULL) {
	#if defined(nginx_version) && (nginx_version >= 8017)
	dd("returning NGX_ERROR");
	return NGX_ERROR;
	#else
	goto failed;
	#endif
	}
	/* TODO add unix sockets */
	last = ngx_snprintf(connstring, len - 1,
	"hostaddr=%V port=%d dbname=%V user=%V password=%V"
	" sslmode=disable",