title: how to use proxy on youtube-dl?
body: <p>I wanna use the proxy and run this
  <code>youtube-dl --proxy socks5://127.0.0.1:1080</code></p>
  
  <p>this is an error below</p>
  
  <p><code>Usage: youtube-dl [OPTIONS] URL [URL...]</code></p>
  
  <p><code>youtube-dl: error: You must provide at least one URL.</code></p>
  
  <p>what is the problem here?</p>