What should I do if I want to record the intermediate results of the task? e.g. {"progress":0.87},I find defination of task states in doc like this

// TaskState represents a state of a task
type TaskState struct {
  TaskUUID  string        `bson:"_id"`
  State     string        `bson:"state"`
  Results   []*TaskResult `bson:"results"`
  Error     string        `bson:"error"`
}

with a slice of result, then how can I return mutlipy result in one task? Or other way to record intermediate results?