title: Storing list of values in the environment variable in declarative Jenkins pipeline
body: <p>I've got the following pipeline but I don't know why it fails on the first line of code:</p>
  
  <pre><code>pipeline {
      agent any
      environment {
          def mypods = []
      }
      stages {
          stage('Getting pods') {
              steps {
                  script {
                     withKubeConfig(caCertificate: '.....', credentialsId: '.....', serverUrl: '.....') {
                         env.mypods = sh "kubectl get pod | grep Running | awk '{print \$1}'"
                      }
                  }
              }
          }
          stage('Print pods') {
              steps {
                  script {
                      mypods.each {
                          println "Item: $it"
                      }
                  }
              }
          }
      }
  }
  </code></pre>
  
  <p>I need to use a list because the kubectl get pods command return a list of pods, so I have to save and use them during the stages.
  How can I create a list on declarative pipeline?
  Thanks in advance.</p>
  
  <p>This is the error:</p>
  
  <pre><code>Running in Durability level: MAX_SURVIVABILITY
  org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
  WorkflowScript: 4: Environment variable values must either be single quoted, double quoted, or function calls. @ line 4, column 22.
             def mypods = []
                          ^
  
  WorkflowScript: 3: No variables specified for environment @ line 3, column 5.
         environment {
         ^
  
  2 errors
  
      at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:310)
      at org.codehaus.groovy.control.CompilationUnit.applyToPrimaryClassNodes(CompilationUnit.java:1085)
      at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:603)
      at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:581)
      at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:558)
      at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:298)
      at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:268)
      at groovy.lang.GroovyShell.parseClass(GroovyShell.java:688)
      at groovy.lang.GroovyShell.parse(GroovyShell.java:700)
      at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell.doParse(CpsGroovyShell.java:131)
      at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell.reparse(CpsGroovyShell.java:125)
      at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.parseScript(CpsFlowExecution.java:560)
      at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.start(CpsFlowExecution.java:521)
      at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:320)
      at hudson.model.ResourceController.execute(ResourceController.java:97)
      at hudson.model.Executor.run(Executor.java:429)
  Finished: FAILURE
  </code></pre>