How can I change the GO version on a none GO build job?

I want to use the latest Go (1.13.1) in a job that has language: cpp set. An older version is already available

Pre-installed Go versions
1.11.1

I’ve already tried to set the TRAVIS_GO_VERSION variable

env:
  global:
    - TRAVIS_GO_VERSION=1.13.1

and calling gimme to install the latest version

gimme 1.13.1

Nothing worked so far

https://travis-ci.org/ElektraInitiative/libelektra/jobs/594018322

eval "$(gimme 1.13.1)" should do the job.

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