title: Map key literal that starts with @ in elixir
body: <p>I'm writing some Elixir code that will make an HTTP POST request, where the body is a JSON document of options.  One of the properties starts with an <code>@</code> symbol.</p>
  
  <p>Not possible:</p>
  
  <pre><code>json = %{ q: "foobar", @timestamp: 1234567890 } |&gt; Poison.encode!
  </code></pre>
  
  <p>What is the correct way to write a map key literal which starts with <code>@</code>?</p>