title: spring rabbitmq unit test result is null
body: <p>I am writing Spring rabbitmq unit test.</p>
  
  <p>However, the result is always null.</p>
  
  <p><code>2020-02-05 11:36:53,113 ERROR o.s.a.rabbit.core.RabbitTemplate - No correlation header in reply</code></p>
  
  <p>These messages are exposed.</p>
  
  <p>What exactly does no correlation header in reply mean?</p>
  
  <p>If check the log of the business logic, the result is returned correctly.</p>
  
  <p>I don't know which one is the problem.</p>
  
  <pre><code>Object result = rabbitTemplate.convertSendAndReceive(exchange, routingKey, requestMap);
  // always result is null
  </code></pre>