title: base_url issues in drf_yasg swagger
body: <p>I am running Django with Nginx in <strong>8000</strong> port. Here Nginx is exposed outside in 8000 port. But in Swagger UI the <strong>base_url</strong> is set as without port. So Swagger is trying to access endpoints without a port, then it gives a response as <strong>TypeError: Failed to fetch</strong>.</p>
  <p><strong>Kindly refer to the below image to know how base_url is set</strong>
  <a href="https://i.stack.imgur.com/uYtOH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uYtOH.png" alt="enter image description here" /></a></p>
  <p><strong>Kindly refer to the below image to know how a request is sent from Swagger</strong>
  <a href="https://i.stack.imgur.com/T5sz4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T5sz4.png" alt="enter image description here" /></a></p>
  <p>When I access the endpoint (with port) using Postman it is working fine. The problem occurs only when I try using Swagger (because is sent a request without port).</p>
  <p>Here I want Swagger to sent all the requests with the port. Please help me to resolve this issue. Thanks.</p>
  <p>Note:</p>
  <ol>
  <li>I'm using the <strong>drf-yasg==1.17.1</strong> package to generate <strong>Swagger UI</strong></li>
  <li>Other requirements are <strong>Django==3.0.3</strong> and <strong>djangorestframework==3.11.0</strong></li>
  </ol>