Gitlab-ci和docker组成：握手超时

我尝试使用Gitlab和docker设置configuration项时出现了一些问题：docker-compose构build失败，并显示错误

Building web Step 1/8 : FROM python:2.7-alpine Service 'web' failed to build: Get https://registry-1.docker.io/v2/: net/http: TLS handshake timeout ERROR: Job failed: exit code 1

这是我的gitlab-runner / config.toml：

 concurrent = 1 check_interval = 0 [[runners]] name = "Backend-django runner" url = "http://gitlab.codewithme.today/ci" token = "4976e4153178a33029e041a0f5fe07" executor = "docker" [runners.docker] tls_verify = false image = "python:2.7-alpine" privileged = true disable_cache = false volumes = ["/cache"] shm_size = 0 [runners.cache] 

我自己的gitlab容器registry使用letsencrypt创build的证书可以正常工作，同样的过程在gitlab runner的同一台服务器上本地成功完成。

这个问题怎么能被克服？