title: Read from parameters in Symfony 3.4 getParameter null
body: <p>I can't read a parameter from <code>parameters.yml</code> in my controller.</p>
  
  <p>I want to do this:</p>
  
  <pre><code>//My Controller
  class ExampleController extends Controller
  {
      function someMethod($argument)
      {
          dump($this-&gt;getParameter('free_proxy'));die();
  </code></pre>
  
  <p>and in parameters.yml I got:</p>
  
  <pre><code>parameters:
      free_proxy: "http://xxx:8080"
  </code></pre>
  
  <p>I get an error: <code>Call to a member function getParameter() on null</code></p>
  
  <p>I've tested some solutions like adding some services and using get and stuff but nothing works.</p>
  
  <p>EDIT: also, I tried this:</p>
  
  <pre><code>services:
      _defaults:
          autowire: true
          autoconfigure: true
          public: false
          bind:
            $freeProxy: '%free_proxy%'
  </code></pre>
  
  <p>Then using:</p>
  
  <pre><code>$this-&gt;container-&gt;getParameter('free_proxy');
  </code></pre>
  
  <p>But I got an error: <code>Unused binding "$freeProxy" in service...</code></p>