code: public Connection getConnection(RpcClient rpcClient, ClientTransportConfig transportConfig, Url url) {
          if (rpcClient == null || transportConfig == null || url == null) {
              return null;
          }
          Connection connection;
          try {
              connection = rpcClient.getConnection(url, url.getConnectTimeout());
          } catch (InterruptedException e) {
              throw new SofaRpcRuntimeException(e);
          } catch (RemotingException e) {
              throw new SofaRpcRuntimeException(e);
          }
          if (connection == null) {
              return null;
          }
  
          return connection;
      }
docs: 通过配置获取长连接
  
  @param rpcClient       bolt客户端
  @param transportConfig 传输层配置
  @param url             传输层地址
  @return 长连接