title: How to iterate Flux and mix with Mono
body: <p>I have a use case when I should send email to the users.
  First I create email body. </p>
  
  <pre><code>Mono&lt;String&gt; emailBody = ...cache();
  </code></pre>
  
  <p>And then I select users and send the email to them:</p>
  
  <pre><code>Flux.fromIterable(userRepository.findAllByRole(Role.USER))
              .map(User::getEmail)
              .doOnNext(email -&gt; sendEmail(email, emailBody.block(), massSendingSubject))
              .subscribe();
  </code></pre>
  
  <p>What I don't like </p>
  
  <ol>
  <li>Without cache() method emailBody Mono calculates in each iteration step. </li>
  <li>To get emailBody value I use emailBody.block() but maybe there's a reactive way and not call block method inside Flux flow?</li>
  </ol>