code: func (c *RPCClient) GetCoordinate(node string) (*coordinate.Coordinate, error) {
  	header := requestHeader{
  		Command: getCoordinateCommand,
  		Seq:     c.getSeq(),
  	}
  	req := coordinateRequest{
  		Node: node,
  	}
  	var resp coordinateResponse
  
  	if err := c.genericRPC(&header, &req, &resp); err != nil {
  		return nil, err
  	}
  	if resp.Ok {
  		return &resp.Coord, nil
  	}
  	return nil, nil
  }
docs: // GetCoordinate is used to retrieve the cached coordinate of a node.