title: Get number of connections of a Transport in Go
body: <p>I am implementing load balancing algorithms for a reverse proxy in Go.</p>
  <p>Of course, <strong>round-robin</strong> was simple, but I am struggling to implement <strong>Least connections</strong>.</p>
  <p>I could not find a way to inspect the number of connections from the proxy to the backends.</p>
  <p>Is there a way to get the number of open connections from the Transport or any other underlying structure?</p>