title: Get a random character from a string and append to another string
body: <p>I'm trying to write the Rust equivalent of the following C++ code:</p>
  
  <pre class="lang-cpp prettyprint-override"><code>result += consonants[rand() % consonants.length()];
  </code></pre>
  
  <p>It is meant to take a random character from the string <code>consonants</code> and append it to the string <code>result</code>.</p>
  
  <p>I seem to have found a working Rust equivalent, but it's... monstrous, to say the least. What would be a more idiomatic equivalent?</p>
  
  <pre><code>format!("{}{}", result, consonants.chars().nth(rand::thread_rng().gen_range(1, consonants.chars().count())).unwrap().to_string());
  </code></pre>