Add Pusher to UK companies using Go.

GoUsers.md

diff --git a/GoUsers.md b/GoUsers.md
index 5f8e31c..78946af 100644
--- a/GoUsers.md
+++ b/GoUsers.md
@@ -532,5 +532,6 @@
   * [Ryanair](http://www.ryanair.com) - [source](https://youtu.be/CWCHT3GClMM?t=15m)
   * [Belua] (https://www.belua.com)
   * [Intern Avenue] (https://www.internavenue.com/)
+  * [Pusher](https://pusher.com) - [github](https://github.com/pusher) [blog](https://blog.pusher.com)
 
 See also [Success Stories](SuccessStories)
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