Not working behind a proxy

[bheisig]

Since version 0.4.0 it's not possible to start the exporter behind a proxy. Output using Docker:

panic: failed to initialize API client. this should never happen!

goroutine 1 [running]:
github.com/anas-aso/ssllabs_exporter/internal/ssllabs.init.0()
        /workdir/internal/ssllabs/analyze.go:34 +0x74

Dockerfile:

FROM anasaso/ssllabs_exporter:latest
ENV http_proxy http://proxy.example.com
ENV https_proxy http://proxy.example.com
ENV HTTP_PROXY http://proxy.example.com
ENV HTTPS_PROXY http://proxy.example.com

Commands:

docker build . -t ssllabs:test
docker run --rm -it -p 19115:19115 ssllabs:test

It's working with version 0.3.0 instead of latest. I've tested versions 0.4.1 and 0.4.0, too. But no luck.

Latest version is working fine on another environment without a proxy.

Thanks for you help.