#Beginner:
How to Write go Code
Gives an overview of how to set up your GOPATH.
A Tour of Go
An in browser, step by step tutorial of Go.
Effective Go
A walkthrough of every Go concept, with examples and tips/tricks.go by example
Go by Example
Explores different programming/Go concepts by providing several examples for each.
Go at Google - Rationale for Go creation by the language creators(from 2012).
#Intermediate:
Understanding and using the vendor folder
Using Go's database/sql package
Using Make to build Go projects
Awesome Go - A curated list of awesome Go frameworks, libraries and software. Inspired by awesome-python.
#Testing:
Interfaces and composition for effective unit testing
5 simple tips for unit tests