std::unique_lock<Mutex>::release
From cppreference.com
                    
                                        
                    < cpp | thread | unique lock
                    
                                                            
                    |   mutex_type* release() noexcept;  | 
(since C++11) | |
Breaks the association of the associated mutex, if any, and *this.
No locks are unlocked. If *this held ownership of the associated mutex prior to the call, the caller is now responsible to unlock the mutex.
Parameters
(none)
Return value
Pointer to the associated mutex or a null pointer if there was no associated mutex.
Example
| This section is incomplete Reason: no example  | 
See also
|   unlocks (i.e., releases ownership of) the associated mutex  (public member function)  |