Support multiple backend, not only from https://dl.google.com/go #277
Description
Please complete the following tasks
goup version
v0.11.1
Describe your use case
We alway use https://dl.google.com/go, In China we need use mirror like aliyun, ustc
Describe the solution you'd like
Provides multiple optional backend
Alternatives, if applicable
No response
Additional Context
No response