最近用到docker，想学习一下，在ubuntu上安装docker后，想下载hello-world测试，结果pull报错：

Using default tag: latest
Error response from daemon: Get "https://registry-1.docker.io/v2/": net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

使用search命令报错：

Error response from daemon: Get "https://index.docker.io/v1/search?q=hello-world&n=25": dial tcp 199.59.149.244:443: connect: connection refused

我已经配置了/etc/docker/daemon.json，也添加了dns：

nameserver 223.5.5.5
nameserver 223.6.6.6