public with sharing class buttonCaseCtl {

    @AuraEnabled
    public static InitData init(String recordId){
        InitData res = new initData();
        try{
            Case report =  [SELECT Id FROM Case WHERE Id =: recordId LIMIT 1];
            System.debug(LoggingLevel.INFO, '*** opp: ' + report);
            res.Id = report.Id;


            System.debug(LoggingLevel.INFO, '*** res: ' + res);
        }catch(Exception e){
            System.debug(LoggingLevel.INFO, '*** e: ' + e);
        }
        return res;
    }   

    public class InitData{
        @AuraEnabled
        public String Id;
     }
}