GCC/Clang treats variables within lambdas as potentially shadowing those outside the lambda, despite them not being captured inside the lambda's capture list.
If this is not waited on, the synchronization primitives are destroyed
whe main exits and the detached task ends up signalling garbage and not
properly finishing.
Since C++17, the introduction of deduction guides for locking facilities
means that we no longer need to hardcode the mutex type into the locks
themselves, making it easier to switch mutex types, should it ever be
necessary in the future.
