Async tasks are not properly shut down

When shutting down the server in PaperMC the following log message is logged

```log
[12:15:59 ERROR]: Nag author: 'Seblii' of 'ServerBackup' about the following: 
This plugin is not properly shutting down its async tasks when it is being shut down. 
This task may throw errors during the final shutdown logs and might not complete before process dies.
```