modify reason: Unresolved reference 'err' (#352)

eBook/13.5.md

@@ -34,7 +34,7 @@ func check(err error) { if err != nil { panic(err) } }
 func errorHandler(fn fType1) fType1 {
 	return func(a type1, b type2) {
 		defer func() {
-			if e, ok := recover().(error); ok {
+			if err, ok := recover().(error); ok {
 				log.Printf(“run time panic: %v”, err)
 			}
 		}()