Nit(build): download dependency unsuccessfully

[zztaki]

Is your feature request related to a problem? (你需要的功能是否与某个问题有关?)

Describe the solution you'd like (描述你期望的解决方法)
mount /etc/hosts to docker

Describe alternatives you've considered (描述你想到的折衷方案)

Additional context/screenshots (更多上下文/截图)
When I build using make build stor=fs dep=1, it will compile etcdclient and download go1.12.8 from golang.google.cn or dl.google.com first.

However, since we did not mount the local hosts to docker. In docker, it may not be able to resolve the correct DNS address, resulting in the failure to successfully download go1.12.8.

I will submit a PR soon :)