Eukaryotes. Eukaryotes are organisms made up of cells that possess a membrane-bound nucleus (that holds genetic material) as well as membrane-bound organelles. Genetic material in eukaryotes is contained within a nucleus within the cell and DNA is organized into chromosomes. Eukaryotic organisms may be multicellular or single-celled organisms. All animals are eukaryotes. Other eukaryotes include plants, fungi, and protists. A typical eukaryotic cell might contain the following parts: plasma membrane; nucleolus
A unique_lock can be created without immediately locking, can unlock at any point in its existence, and can transfer ownership of the lock from one instance to another. So you always use lock_guard, unless you need the capabilities of unique_lock. A condition_variable needs a unique_lock.
I'm not sure why this is async. Unless you have a good reason for write to the file asynchronously, this is wasted effort. If you lock properly, this will work fine. Your locker variable should be marked static. think every unit test has it's own file so the lock on its own should be sufficient. If that's not the case, come to think of it, this try again method would probably be overwhelm and it would have to be a static lock.