title: How to echo message at telegram /start?
body: <p>I'd like to set up a authentication through telegram using it's <a href="https://core.telegram.org/bots#deep-linking" rel="nofollow noreferrer">deep linking</a> api.</p>
  
  <p>In order to authenticate, in my app I ask users to click on a link like:</p>
  
  <pre><code>https://telegram.me/myloginbot?start=somesecretkey
  </code></pre>
  
  <p>If I understand the docs correctly, I should expect the bot to echo back <code>somesecretky</code> to my server. </p>
  
  <p>Now, this step of the docs is unclear to me:</p>
  
  <blockquote>
    <ol start="6">
    <li>Configure the webhook processor to query Memcached with the parameter that is passed in incoming messages beginning with /start</li>
    </ol>
  </blockquote>
  
  <p>If I understand correctly, I need to configure <code>myloginbot</code> so that when the user clicks start button on the bot's page, the bot echos back to my server a url containing  <code>somesecretkey</code> and some user info. But I don't know how to do so. </p>
  
  <p>In <a href="https://stackoverflow.com/a/31212577/5779769">this</a> answer, it is suggested that:</p>
  
  <blockquote>
    <ol start="6">
    <li>Let the bot retrieve the username by querying the database or key-value storage for unique_code.</li>
    </ol>
  </blockquote>
  
  <p>But I don't know how can I make the bot query the (presumably remote) database.</p>
  
  <p>So really appreciate your hints. </p>