Apex Sample REST Callout

MyServiceAPI.cls

public with sharing class MyServiceAPI {

    @AuraEnabled
    public static String getTransactions(String dateFrom) {

            HttpRequest req = new HttpRequest();
            req.setMethod('GET');
            //retrieved from named credentials
            request.setEndpoint('callout:MyServiceAPI/transactions?date=dateFrom');
            req.setEndpoint(strEndPoint);
            req.setHeader('Accept', 'application/json');
            Http h = new Http();
            HTTPResponse res = h.send(req);

            if (res.getStatusCode() == 200) {
                return res.getBody();
            }
        return null;
    }

}