server.go
func (s *Server) Wait() {
	s.conns.Range(func(c interface{}) {
		c.(*Conn).Wait(180)
	})
}
func (s *Server) Wait() {
	s.conns.Range(func(c interface{}) {
		c.(*Conn).Wait(180)
	})
}
// Wait waits for all message/connection handler goroutines in all connections to exit.