conn.go
func (c *Conn) Middleware(middleware ...Middleware) {
	for _, m := range middleware {
		c.MiddlewareFunc(m.Middleware)
	}
}
func (c *Conn) Middleware(middleware ...Middleware) {
	for _, m := range middleware {
		c.MiddlewareFunc(m.Middleware)
	}
}
// Middleware registers middleware to handle incoming request messages.