my $tx = $ua->build_tx(POST => 'https://android.googleapis.com/gcm/send' => $headers =>
                               form => { registration_id => 'APA',
                                         collapse_key    => 'foo',
                                         'data.payload'  => $payload } );
        $tx = $ua->start($tx);

-- Blocking request (https://android.googleapis.com/gcm/send)
-- Connect 10f7c2dc01008c9f8faa34b4b1bf7bbd (https://android.googleapis.com:443)
-- Client >>> Server (https://android.googleapis.com/gcm/send)
POST /gcm/send HTTP/1.1\x0d
User-Agent: Mojolicious (Perl)\x0d
Connection: keep-alive\x0d
Content-Type: application/x-www-form-urlencoded\x0d
Accept-Encoding: gzip\x0d
Content-Length: 407\x0d
Host: android.googleapis.com\x0d
Authorization: key=Ac\x0d
\x0d
collapse_key=foo&data.payload=%7B%22android%22:%7B%22alert%22:%22alerthere%22,%22badge%22:%22%2B2%22,%22title%22:%22titlehere%22,%22tickerText%22:%22foo+bar+long+crap+here+blah+blah+blah%22%7D,%22token%22:1234,%22msgtype%22:1%7D&registration_id=AP
-- Client <<< Server (https://android.googleapis.com/gcm/send)
HTTP/1.1 200 OK\x0d
Content-Type: text/plain; charset=UTF-8\x0d
Date: Sat, 21 Mar 2015 03:11:01 GMT\x0d
Expires: Sat, 21 Mar 2015 03:11:01 GMT\x0d
Cache-Control: private, max-age=0\x0d
X-Content-Type-Options: nosniff\x0d
X-Frame-Options: SAMEORIGIN\x0d
X-XSS-Protection: 1; mode=block\x0d
Server: GSE\x0d
Alternate-Protocol: 443:quic,p=0.5\x0d
Accept-Ranges: none\x0d
Vary: Accept-Encoding\x0d
Transfer-Encoding: chunked\x0d
\x0d
26\x0d
id=0:14218cc6\x0d
0\x0d

        my $tx = $ua->build_tx(POST => 'https://android.googleapis.com/gcm/send' => $headers =>
                               form => { registration_id => 'APA',
                                         collapse_key    => 'foo',
                                         'data.payload'  => $payload } );
        $tx = $ua->start($tx => sub{});

        -- Non-blocking request (https://android.googleapis.com/gcm/send)
        -- Connect ea59f7dbaab5118a80d680892718e8aa (https://android.googleapis.com:443)