exit with err if cancelled and newline

main.go

@@ -34,9 +34,19 @@ func main() {
 	}
 
 	for alert := range alerts {
+		if ctx.Err() != nil {
+			break
+		}
 		if err := alertAt(ctx, *ntfy, time.Now(), alert, time.Now().Format("15:04")); err != nil && ctx.Err() == nil {
 			panic(err)
 		}
+		if ctx.Err() != nil {
+			break
+		}
+	}
+
+	if err := ctx.Err(); err != nil {
+		os.Exit(1)
 	}
 }
 
@@ -64,6 +74,7 @@ func alertsAfter(ctx context.Context, dur time.Duration) (chan string, error) {
 			case <-time.After(time.Second):
 			}
 		}
+		fmt.Println()
 		ch <- "alerting after " + dur.String()
 	}()
 	return ch, nil