Sharding tests do not work (using default settings)

[mdashti]

Describe the bug

To Reproduce
Steps to reproduce the behavior:

1. Switch to the recent commit on main @ 9d1c46a
2. Follow the instructions in the https://github.com/postgresml/pgcat/blob/main/tests/sharding/README.md

• start a postgres server
• run psql -f query_routing_setup.sql
• start up PgCat by running cargo run --release in the root of the repo
• run psql -h 127.0.0.1 -p 6432 -f query_routing_test_insert.sql
  - this command does not work, and I run this one instead: PGPASSWORD=sharding_user psql sharded_db -h 127.0.0.1 -p 6432 -U sharding_user -f query_routing_test_insert.sql

Expected behavior
It's expected for the test to run successfully. However, it fails with:

SET SHARDING KEY
INSERT 0 1
psql:query_routing_test_insert.sql:6: ERROR:  syntax error at or near "KEY"
LINE 1: SET SHARDING KEY TO '2';
                     ^

Desktop

• OS: macOS
• Version: 1.1.1 (main @ 9d1c46a)

[mdashti]

This diff fixes the issue:

diff --git a/pgcat.toml b/pgcat.toml
index 3e8801b..d8ed108 100644
--- a/pgcat.toml
+++ b/pgcat.toml
@@ -270,7 +270,7 @@ username = "sharding_user"
 # if `server_password` is not set.
 password = "sharding_user"
 
-pool_mode = "session"
+pool_mode = "transaction"
 
 # PostgreSQL username used to connect to the server.
 # server_username = "another_user"

[levkk]

Could you submit a PR with the fix if you have a moment?