Fix data race

[AnkushinDaniil]

This pull request includes a small but important change to the Run method in the rpc/handlers.go file. The change ensures thread safety by locking and unlocking a mutex around the loop that waits for all subscriptions to complete.

Reason for the Change:

During testing, I encountered a panic that occurred intermittently—sometimes the tests would pass, and other times they would fail unpredictably. This behavior was caused by concurrent access to the map of active subscriptions during iteration, resulting in a race condition. Such issues are common in Go when shared resources are accessed by multiple goroutines without proper synchronization.

Solution:

To address this, I added a mutex lock around the loop that processes subscriptions.

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.59%. Comparing base (2653ae9) to head (7594251).

Files with missing lines	Patch %	Lines
rpc/handlers.go	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2363      +/-   ##
==========================================
+ Coverage   74.52%   74.59%   +0.06%     
==========================================
  Files         110      110              
  Lines       11908    11913       +5     
==========================================
+ Hits         8875     8887      +12     
+ Misses       2343     2338       -5     
+ Partials      690      688       -2     

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