public with sharing class CASCsvRecordsController {

    class CSVBody{
        
        List<List<String>> csvRows {get;set;}
        
        List<String> csvHeader {get;set;}
    }
    
    @AuraEnabled
    public static CSVBody loadCSV(String csv){
        

        //The CASConnector connect with a REST server and get the CSV as String
        String fullcsvbody = CASConnector.getCSV('293880', '419356');
        
        CSVBody csvBodyObj = new CSVBody();
        
        //This is List<String> of the CSV header
        csvBodyObj.csvRows = CASCsv.getCSVRows(fullcsvbody);
        
        //This is a List<List<String>> of the line & column
        csvBodyObj.csvHeader = CASCsv.getCSVHeader(fullcsvbody);
       
        return csvBodyObj;
    }

}

({
 onLoad: function(component, event) {
  console.log('onLoad call');
  
  //call apex class method
  var loadHeader = component.get('c.loadCSV');
  loadHeader.setCallback(this, function(response) {
   //store state of response
   var state = response.getState();
   if (state === "SUCCESS") {
       
    component.set('v.ListOfHeader', response.getReturnValue());

   }
      else{
          console.log("cas Failed with state: " + state);
      }
  });
  $A.enqueueAction(loadHeader);
 },
 
})

<aura:component controller="CASCsvRecordsController" >
   <!--aura init handler , call js "loadContactList" function on component load, and display contact data on table-->   
   <aura:handler name="init" value="{!this}" action="{!c.loadCsvList}"/>
    
   <aura:attribute name="ListOfHeader" type="List" />