Set GOPROXY=direct by default in docker images for 1.3+

[tamalsaha]

Due to various privacy concerns, can you set GOPROXY=direct by default in docker images for 1.3+ ?

Thanks.

[yosifkit]

We aren't going to change the default provided in Go releases (https://proxy.golang.org). See their privacy page https://proxy.golang.org/privacy and evaluate whether this is acceptable for your use case (as with any hosted service).

There a quite a few others providing a similar service and self-hosted options too: https://github.com/golang/go/wiki/Modules#are-there-always-on-module-repositories-and-enterprise-proxies