Improvement suggestion: locking shdict keys

As you might know: Session management without a locking mechanism can lead to data-corruption as parallel requests will cause race-conditions. Please add this feature:

res=shdict:lock_key(key);
res=shdict:unlock_key(key);

And for performance-reasons a combined command for the most obvious tasks:

data, res=shdict:lock_key_and_get(key);
res=shdict:set_and_unlock_key(key, data);

and do an auto-unlock for all keys still being locked for that request when the Lua-script ends.

Maybe one could also allow a security-auto-unlock after 30 seconds.
You just put a new int into your shdict node-structure and when it is 0 it is unlocked.
When it contains a timestamp > 0 it is locked and when now-timestamp>30 then ignore this previous lock when trying to lock it.
Locktime-limit can be set as second parameter in lock_key(key, lock_timeout) and lock_key_and_get(key, lock_timeout).

Start by locating the shdict node structure and the entry points for shdict operations and Lua-script request cleanup. Define the locking, timeout, combined-operation, and automatic-unlock behavior, then verify the feature across parallel requests and expired locks.