title: How to use "cache" method of Mono
body: <p>I'm a beginner of spring webflux. While researching I found some code like:</p>
  <pre><code>Mono result = someMethodThatReturnMono().cache();
  </code></pre>
  <p>The name &quot;cache&quot; tell me about caching something, but where is the cache and how to retrieve cached things? Is it something like caffeine?</p>