title: Docker postgres change username and password
body: <p>I am using the <a href="https://hub.docker.com/r/mdillon/postgis/" rel="nofollow noreferrer"><code>mdillon/postgis</code></a> image as my containerized database. I have created a database that is owned by a user I created using the image's username and password environment variables. Now I need to changes that user's username and password.</p>
  <p>I successfully changed the password but I could not change the username because you can change the current user's username.</p>
  <p>I tired logging in as the <code>postgres</code> user but I get an error saying theres is no such user.</p>
  <p>Any ideas?</p>