mex.go
func newMessageExchangeSet(log Logger, name string) *messageExchangeSet {
	return &messageExchangeSet{
		name:             name,
		log:              log.WithFields(LogField{"exchange", name}),
		exchanges:        make(map[uint32]*messageExchange),
		expiredExchanges: make(map[uint32]struct{}),
	}
}
func newMessageExchangeSet(log Logger, name string) *messageExchangeSet {
	return &messageExchangeSet{
		name:             name,
		log:              log.WithFields(LogField{"exchange", name}),
		exchanges:        make(map[uint32]*messageExchange),
		expiredExchanges: make(map[uint32]struct{}),
	}
}
// newMessageExchangeSet creates a new messageExchangeSet with a given name.