code: func (r *request) setWriteOptions(q *WriteOptions) {
  	if q == nil {
  		return
  	}
  	if q.Datacenter != "" {
  		r.params.Set("dc", q.Datacenter)
  	}
  	if q.Token != "" {
  		r.params.Set("token", q.Token)
  	}
  }
docs: // setWriteOptions is used to annotate the request with
  // additional write options