Merge pull request #13 from amrlabib/fix/#12

use calculateExpiryDate in useTimer interval instead of subtractSecond

Author: amrlabib

src/useTimer.js

@@ -63,7 +63,7 @@ export default function useTimer(settings) {
   function start() {
     if(isValidExpiryTimestamp(expiryTimestamp) && !intervalRef.current) {
       calculateExpiryDate();
-      intervalRef.current = setInterval(() => subtractSecond(), 1000);
+      intervalRef.current = setInterval(() => calculateExpiryDate(), 1000);
     }
   }