@AuraEnabled
    public static List<reasonObject> getReasonRest(Id eId){
        System.debug(eId);
        Map<String,String> sessionAttributes = Auth.SessionManagement.getCurrentSession();
        System.debug('Session '+sessionAttributes.get('SessionId'));
        Id rType = [SELECT id, RecordTypeId FROM Case WHERE ID = :eId].RecordTypeId;
        Http http = new Http();
        HttpRequest request = new HttpRequest();
        String host = System.Url.getSalesforceBaseURL().toExternalForm();
        String url = host + '/services/data/v43.0/ui-api/object-info/Case/picklist-values/'+rType+'/Reason';
        //String url = host + '/ui-api/object-info/Case/picklist-values/'+rType+'/Reason';
        System.debug(url);
        request.setEndpoint(url);
        request.setMethod('GET');  
        request.setHeader('Authorization', 'OAuth '+sessionAttributes.get('SessionId'));
        HttpResponse response;        
        response = http.send(request);
        System.debug('response ' + response);
        Map<String, Object> meta = (Map<String, Object>) JSON.deserializeUntyped(response.getBody());
        system.debug(meta);
		List<reasonObject> optionsList = new List<reasonObject>();
        //optionsList.add(new SelectOption('--None--', ''));
        if(meta.containsKey('values')){                                
                for(Object o: (List<Object> )meta.get('values')){
                    Map<String, object > temp = (Map<String, object>)o;        
                    System.debug((String)temp.get('label')+ ' ' + (String)temp.get('value'));
                    reasonObject ro = new reasonObject();
                    ro.label=(String)temp.get('label');
                    ro.value=(String)temp.get('value');
                    //optionsList.add(new SelectOption((String)temp.get('label'), (String)temp.get('value')));
                    optionsList.add(ro);
                }
            }
        return optionsList;
    }

System.HttpResponse[Status=Unauthorized, StatusCode=401]