Add link to Go contribution quickstart article (#622)

Author: grokify

README.md

@@ -432,6 +432,7 @@ Here are some companies/projects (alphabetical order) using OpenAPI Generator in
 - 2018/06/08 - [Swagger Codegen is now OpenAPI Generator](https://angular.schule/blog/2018-06-swagger-codegen-is-now-openapi-generator) by [JohannesHoppe](https://github.com/JohannesHoppe)
 - 2018/06/21 - [Connect your JHipster apps to the world of APIs with OpenAPI and gRPC](https://fr.slideshare.net/chbornet/jhipster-conf-2018-connect-your-jhipster-apps-to-the-world-of-apis-with-openapi-and-grpc) by [Christophe Bornet](https://github.com/cbornet) at [JHipster Conf 2018](https://jhipster-conf.github.io/)
 - 2018/06/27 - [Lessons Learned from Leading an Open-Source Project Supporting 30+ Programming Languages](https://speakerdeck.com/wing328/lessons-learned-from-leading-an-open-source-project-supporting-30-plus-programming-languages) - [William Cheng](https://github.com/wing328) at [LinuxCon + ContainerCon + CloudOpen China 2018](https://www.lfasiallc.com/events/lc3-2018/)
+- 2018/07/19 - [OpenAPI Generator Contribution Quickstart - RingCentral Go SDK](https://medium.com/ringcentral-developers/openapi-generator-for-go-contribution-quickstart-8cc72bf37b53) by [John Wang](https://github.com/grokify)
 
 ## [6 - About Us](#table-of-contents)