Used shields.io for the slack badge in the README file. Fixes
# Awesome Go
-[![Build Status](https://travis-ci.org/avelino/awesome-go.svg?branch=master)](https://travis-ci.org/avelino/awesome-go) [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg)](https://github.com/sindresorhus/awesome) [![Slack Widget](https://camo.githubusercontent.com/984828c0b020357921853f59eaaa65aaee755542/68747470733a2f2f73332e65752d63656e7472616c2d312e616d617a6f6e6177732e636f6d2f6e6774756e612f6a6f696e2d75732d6f6e2d736c61636b2e706e67)](http://gophers.slack.com/messages/awesome)
+[![Build Status](https://travis-ci.org/avelino/awesome-go.svg?branch=master)](https://travis-ci.org/avelino/awesome-go) [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg)](https://github.com/sindresorhus/awesome) [![Slack Widget](https://img.shields.io/badge/join-us%20on%20slack-gray.svg?longCache=true&logo=slack&colorB=red)](http://gophers.slack.com/messages/awesome)
A curated list of awesome Go frameworks, libraries and software. Inspired by [awesome-python](https://github.com/vinta/awesome-python).
