code: func (a *customAdapter) sendMessage(ctx *customAdapterWorkerContext, req interface{}) error {
  	b, err := json.Marshal(req)
  	if err != nil {
  		return err
  	}
  	a.Trace("xfer: Custom adapter worker %d sending message: %v", ctx.workerNum, string(b))
  	// Line oriented JSON
  	b = append(b, '\n')
  	_, err = ctx.stdin.Write(b)
  	return err
  }
docs: // sendMessage sends a JSON message to the custom adapter process