"Go is a programming language designed by Google to help solve Google's problems." So said Rob Pike, one of the Go language's designers.
That may be the case, yet the open source language is increasingly being adopted by enterprises around the world for building applications at large scale.
The story is similar with Erlang. Originally a proprietary language developed by Swedish telecommunications company Ericsson for handling massive volumes of telephone switching data on its hardware, Erlang was open sourced and is now rapidly gaining popularity for large-scale applications.
And there's more. Facebook developed GraphQL and BigPipe technologies in response to the particular challenges it faces running a social network processing hundreds of billions of API calls a day for over 1.5 billion active members. Today these technologies have been open sourced, and are used by the likes of content management project Drupal to make its mobile web pages load faster.