x509 cert error when using GOPROXY in Dockerfile

Question

Seems like this should be easy but for some reason I'm making heavy weather of it. I have private (corp) network that is giving me GOPROXY services: "https://my.corp.network/repository/golang"

In my Dockefile I have:

ENV GOPROXY=https://my.corp.network/repository/golang
COPY . .
RUN go mod download

The docker build is erroring out with this: "https://sum.golang.org/{path} x509: certificate signed by unknown authority"

Isn't the whole purpose of GOPROXY to shield me from having to interact with Internet-based sources for my go modules?

When I am not using Docker , and my go environment has this: GOPROXY="https://my.corp.network/repository/golang" , I can use go get -u github.com/gofiber/fiber/v2 and this works fine and I build my local smoke test environment.

Why is this then failing when I go to containerize the process using Docker?

Answer 1

@SteffenUllrich was correct to point out that the issue was a lack of a valid certificate. I found an image in our local corp repository that as the corp cert setup properly, and from there the rest of the Go implementation was fine.