g.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Go 360Go Skyway</title>
  <meta name="description" content="Go to 360 Video — A-Frame Skyway">
</head>

<body onload="setFocusToRoom()">
  <h1>Go to 360Go Skyway</h1>
  <form id="form_go" action="go.html" method="GET">
    Room:<input id="roomname_text" name="room" type="text" size="32" value="go5394"></input>
    <input type="submit"></input>
  </form>

  <script>
    document.onkeydown = function (event) {
      if (event.keyCode == 13) {
        document.getElementById('form_go').submit();
      }
    };

    function setFocusToRoom() {
      const input =  document.getElementById('roomname_text');
      const len = input.value.length;
      input.focus();
      input.setSelectionRange(len, len);
    }
  </script>
</body>
</html>