title: I am getting the error: 'docker: invalid reference format'
body: <p>This is my command:</p>
  <pre><code>docker run --name online-exam-db \
      -p 5432:5432 \
      -e POSTGRES_DB=online-exam \
      -e POSTGRES_PASSWORD=0NLIN3-ex4m \
      -d postgres
  </code></pre>
  <p>I have researched a lot and I am not finding a solution. I am doing the following tutorial where I also got the command from: <a href="https://auth0.com/blog/using-python-flask-and-angular-to-build-modern-apps-part-1/" rel="nofollow noreferrer">https://auth0.com/blog/using-python-flask-and-angular-to-build-modern-apps-part-1/</a></p>
  <p>I appreciate your help in advance!</p>