To browse full documentation locally, run:

$ godoc -http=localhost:9000

Then open localhost:9000 in the browser. It’ll show the same information as https://golang.org/doc/.

You can run guided tour locally with:

$ go get golang.org/x/tour/gotour
$ go tool tour

This runs https://tour.golang.org/ locally.

You can use godoc for quick reference. For example, to see documentation for fmt.Print:

$ godoc cmd/fmt Print

General help is also available from the command-line:

$ go help [command]

For example, to see documentation for go build use go help build.