code: func (d *Dialer) CloseAll() {
  	d.mu.Lock()
  	conns := d.conns
  	d.conns = make(map[*closableConn]struct{})
  	d.mu.Unlock()
  
  	for conn := range conns {
  		conn.Close()
  	}
  }
docs: // CloseAll forcibly closes all tracked connections.
  //
  // Note: new connections may get created before CloseAll returns.