code: func WalkTaskStatus(tx *bolt.Tx, fn func(id string, status *api.TaskStatus) error) error {
  	bkt := getTasksBucket(tx)
  	if bkt == nil {
  		return nil
  	}
  
  	return bkt.ForEach(func(k, v []byte) error {
  		tbkt := bkt.Bucket(k)
  
  		p := tbkt.Get(bucketKeyStatus)
  		var ts api.TaskStatus
  		if err := proto.Unmarshal(p, &ts); err != nil {
  			return err
  		}
  
  		return fn(string(k), &ts)
  	})
  }
docs: // WalkTaskStatus calls fn for the status of each task.