title: How to multiply duration by integer?
body: <p>To test concurrent goroutines, I added a line to a function to make it take a random time to return (up to one second)</p>
  
  <pre><code>time.Sleep(rand.Int31n(1000) * time.Millisecond)
  </code></pre>
  
  <p>However when I compiled, I got this error</p>
  
  <blockquote>
    <p>.\crawler.go:49: invalid operation: rand.Int31n(1000) * time.Millisecond (mismatched types int32 and time.Duration)</p>
  </blockquote>
  
  <p>Any ideas? How can I multiply a duration?</p>