Get username logged in Jenkins from Jenkins Workflow (Pipeline) Plugin

To make it work with Jenkins Pipeline:

Install user build vars plugin

Then run the following:

pipeline {
  agent any

  stages {
    stage('build user') {
      steps {
        wrap([$class: 'BuildUser']) {
          sh 'echo "${BUILD_USER}"'
        }
      }
    }
  }
}

Did you try installing the Build User Vars plugin? If so, you should be able to run

node {
  wrap([$class: 'BuildUser']) {
    def user = env.BUILD_USER_ID
  }
}

or similar.