Fix signaler not exiting on cancel

`break` is incorrect here, as it just breaks out of the select.
`return` to exit the function instead.

Fixes #1636.

cmd/root.go

@@ -111,7 +111,7 @@ func startSignaler() (func() error, func(err error)) {
 					}
 					log.Info(ctx, "Triggered scan complete", "elapsed", time.Since(start).Round(100*time.Millisecond))
 				case <-ctx.Done():
-					break
+					return nil
 				}
 			}
 		}, func(err error) {