feat: add loom test

[kemingy]

Describe the feature

loom is a testing tool for concurrent Rust code.

Check the doc: https://docs.rs/loom/latest/loom/

Why do you need this feature?

Due to the previous deadlock bug:

• fix: hold one lock at a time to avoid the deadlock in nested function #316
• fix: resolve deadlock when lots of client requests closed before response #311

Additional context

• refer to https://github.com/jonhoo/left-right/blob/main/tests/loom.rs