code: func (tx *Tx) Check() <-chan error {
  	ch := make(chan error)
  	go tx.check(ch)
  	return ch
  }
docs: // Check performs several consistency checks on the database for this transaction.
  // An error is returned if any inconsistency is found.
  //
  // It can be safely run concurrently on a writable transaction. However, this
  // incurs a high cost for large databases and databases with a lot of subbuckets
  // because of caching. This overhead can be removed if running on a read-only
  // transaction, however, it is not safe to execute other writer transactions at
  // the same time.