title: How to insert element at the beginning of a slice?
body: <p>I have a slice:</p>
  <pre><code>mySlice := []int{4,5,6,7}
  myelement := 3
  </code></pre>
  <p>I want to insert <code>myelement</code> at index <code>0</code> so that my output will be <code>[3,4,5,6,7]</code>.</p>
  <p>How can I do that?</p>