code: func (p *Producer) backoff(failed int) {
  	backoff := p.Backoff.Duration()
  
  	p.Logger.WithFields(log.Fields{
  		"failures": failed,
  		"backoff":  backoff,
  	}).Warn("put failures")
  
  	time.Sleep(backoff)
  }
docs: // calculates backoff duration and pauses execution