State的构造

type State struct { Running bool Pid int ExitCode int StartedAt time.Time //# 状态变化锁 stateChangeLock sync.Mutex //# Condition stateChangeCond sync.Cond }

Container的方法
==================
``` golang
// String 返回状态的可读描述
func (s *State) String() string {
    if s.Running {
        return fmt.Sprintf("Up %s", HumanDuration(time.Now().Sub(s.StartedAt)))
    }
    return fmt.Sprintf("Exit %d", s.ExitCode)
}

func (s *State) setRunning(pid int) {
    s.Running = true
    s.ExitCode = 0
    s.Pid = pid
    s.StartedAt = time.Now()
    s.broadcast()
}

func (s *State) setStopped(exitCode int) {
    s.Running = false
    s.Pid = 0
    s.ExitCode = exitCode
    s.broadcast()
}

//# broadcast 解除`Condition`等待
func (s *State) broadcast() {
    s.stateChangeLock.Lock()
    s.stateChangeCond.Broadcast()
    s.stateChangeLock.Unlock()
}

//# wait 设置`Condition`等待
func (s *State) wait() {
    s.stateChangeLock.Lock()
    s.stateChangeCond.Wait()
    s.stateChangeLock.Unlock()
}