LicenseManagement doesn't support Go Modules

The current version of license_management ships Go 1.10, which doesn't support Go Modules. The latest version (5.5.2 as of today) has Go 1.11 built-in. Nevertheless, the default configuration won't work out of the work with go projects using Modules:

$ docker run \  
  -it --volume "$PWD":/code \
  --rm \
  registry.gitlab.com/gitlab-org/security-products/license-management:latest analyze /code
/code /
/gopath/src/app /code /
go get: warning: modules disabled by GO111MODULE=auto in GOPATH/src;
        ignoring go.mod;
        see 'go help modules'
[...]

It's working fine when setting up SETUP_CMD to export GO111MODULE=on; go get. We should detect projects using modules, and enable the support for them automatically.

/cc @bikebilly