Centos7 dockers download mirror error: Get https://registry-1.docker.io/v2/: net / http: request canceled

docker: Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled (Client.Timeout exceeded while awaiting headers).

Solution:
1) create daemon.json file
vim /etc/docker/daemon.json
2) writes:

{
    "registry-mirrors":["https://docker.mirrors.ustc.edu.cn"]
}

3) Restart:

[root@km docker]# systemctl daemon-reload 
[root@km docker]# systemctl restart docker

4) problem is solved.