Too slow building

[George-Chia]

Downloading 10 crates, remaining bytes: 30.6MiB

It wastes about half a day.

[George-Chia]

set image for Chinese users:

.cargo/config.toml

[source.crates-io]
replace-with = 'ustc'

[source.ustc]
registry = "https://mirrors.ustc.edu.cn/crates.io-index/"