title: set_by_lua & os.getenv within openresty:alpine docker container
body: <p>I'm running <code>openresty</code> nginx within <a href="https://hub.docker.com/r/openresty/openresty/" rel="nofollow noreferrer">official</a> <code>alpine-fat</code> docker image, and openresty process starts with <code>nobody</code> user.</p>
  
  <p>I need to set nginx variable with the next string:</p>
  
  <pre><code>set_by_lua $var 'return os.getenv("ENV_VAR")';
  </code></pre>
  
  <p><code>docker-compose.yml</code> contains the next block:</p>
  
  <pre><code>build:
    context: .
    dockerfile: ./Dockerfile.nginx
  environment:
    - ENV_VAR=value
  </code></pre>
  
  <p>But, nginx worker process seems not getting its value, and <code>$var</code> remains empty. </p>
  
  <p>I tried to add <code>export ENV_VAR=value</code> to <code>/etc/profile</code> file, but no use.
  I tried to run openresty with <code>nginx</code> user, but it also can't see the value of <code>ENV_VAR</code> variable.</p>
  
  <p>How can I make that thing work, if I can?</p>