Go is a fairly simple language and the best resources for learning it are online.
For a very gentle (if slow) introduction, you can go through the Go tour (you may wish to skip around).
The fastest way to ramp up on Go, though, is probably to read Effective Go end-to-end. This describes most of the language as well as common patterns and best practices.
How to Write Go Code shows the typical code organization and package structure.
After that, you are probably ready to dive into Go code. If you're looking for more references, some of them are listed here.
Donovan & Kernighan's The Go Programming Language is the best book written about the language (I wouldn't bother with any other books).
The golang.org blog posts are well-written and useful. Some of the more important posts are linked below.
The Go spec is very approachable as far as language specifications go and it should be on your shortlist of go-to references if you have a question about the language.
Finally, for getting into more technical details of the language, here are some useful links:
- Go Slices: usage and internals
- Profiling Go Programs
- The Laws of Reflection
- Arrays, slices (and strings): The mechanics of 'append'
- Go Data Structures and Go Data Structures: Interfaces are two old, but not outdated blog posts by Russ Cox that are very useful references for the internal memory layout of Go data structures.