NewCyclicDoubleBarrier 新建一个可重用的双次栅栏 CyclicDoubleBarrier.

NewEtcdSync 返回一个新的EtcdSync对象.

CyclicDoubleBarrier is a synchronizer that allows a set of goroutines to wait for each other to enter, and wait for each other to leave.

EtcEtcdSync 代表一个基于Redis的分布式并发原语管理器，底层维护和etcd的连接.

Map is like a Go map[interface{}]interface{} but is safe for concurrent use by multiple goroutines without additional locking or coordination.

ReentrantLock is held by the goroutine last successfully locking, but not yet unlocking it.

Barrier 代表一个分布式栅栏对象,类似标准库中的sync.WaitGroup,可以实现分布式的任务编排.

Barrier 代表一个分布式双次栅栏对象.

Mutex 代表一个排他锁对象，比sync.Locker更多的方法.

RWMutex is a reader/writer mutual exclusion lock.