code: func (m *model) closeConns(devs []protocol.DeviceID, err error) {
  	conns := make([]connections.Connection, 0, len(devs))
  	m.pmut.Lock()
  	for _, dev := range devs {
  		if conn, ok := m.conn[dev]; ok {
  			conns = append(conns, conn)
  		}
  	}
  	m.pmut.Unlock()
  	for _, conn := range conns {
  		conn.Close(err)
  	}
  }
docs: // closeConns will close the underlying connection for given devices