nsync package provides a set of primitives that are not provided by standard Go library. NamedMutex - a map of dynamically created mutexes by a referred name. OnceMutex - very similar to sync.Once, however, it is a mutex not a function wrapper. NamedOnceMutex - a map of dynamically created mutexes that can be acquired only once. However, once mutex unlocked it is removed from the map. So, next attempt to acquire this mutex will succeed. Semaphore - a semaphore primitive that can be acquired limited number of times. TryMutex - A mutex that provide ability to set a timeout to acquire a lock. ControlWaitGroup - a controlled goroutine executor that can limit the number concurrently running goroutines. Can help to solve a resource exhaustion problem. SyncFlag - an atomic flag that is wrapped by mutex. Mutex can be set/unset separately to prevent the flag from being set/unset.