I was looking over The Changelog weekly newsletter and one of the topics was Sourcegraph plugin for your editor.
Sourcegraph is a plugin for Go and Sublime Text and Vim but they are working on other languages. Basically, in your editor, you write a bit of code that you may not be clear on. Using Sourcegraph, you can tap into premier open source projects to help you understand a bit of code. There are thousands upon thousands of projects in Sourcegraph.