active choice and file parameters

[Thomas Reifferscheid]

Hi all - 

Can someone please provide clear instructions on how to use AC Reactive Reference Parameter and dynamically render 3 file input parameters that would load the selected file and pass it as base64 encoded string. 

No matter what I do I always end up with empty variables inside the Jenkinsfile. 

https://issues.jenkins.io/browse/JENKINS-38893 has some hints however I fail to get it to work. 

Thanks

Thomas