`make container-build` support GOPROXY env

[FOWind]

Related issue: #295

1. Modify makefile to support GOPROXY on container-build command
2. Add GOPROXY use case in README

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[FOWind]

/assign @rifelpet

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[abctaylor]

Just some thoughts: the front page README references goproxy.io. Some further digging shows it's sponsored by an entity called yunzhanghu.com.

There are k8s estates out there with very stringent infosec requirements. When I was reading the build instructions, I stopped with the project after being told to use goproxy.io and investigating it a bit further. I have no particular view on yunzhanghu.com which may be a CDN goproxy.io uses, and I'd be as cynical for any third party service telling me to proxy all my Go dependencies via a third party.

I get why it exists (for users who are struggling due to "Great Firewall" issues, but this may be limiting adoption of what might be a good project.

[FOWind]

Just some thoughts: the front page README references goproxy.io. Some further digging shows it's sponsored by an entity called yunzhanghu.com.

There are k8s estates out there with very stringent infosec requirements. When I was reading the build instructions, I stopped with the project after being told to use goproxy.io and investigating it a bit further. I have no particular view on yunzhanghu.com which may be a CDN goproxy.io uses, and I'd be as cynical for any third party service telling me to proxy all my Go dependencies via a third party.

I get why it exists (for users who are struggling due to "Great Firewall" issues, but this may be limiting adoption of what might be a good project.

I think you're right. I will update the readme file to remove the specific goproxy uri by a PR.