go doc

The built-in go documentation viewer.

$ go doc strings                # View simplified documentation for the strings package
$ go doc -all strings           # View full documentation for the strings package
$ go doc strings.Replace        # View documentation for the strings.Replace function
$ go doc sql.DB                 # View documentation for the database/sql.DB type
$ go doc sql.DB.Query           # View documentation for the database/sql.DB.Query method
$ go doc -src strings.Replace   # View the source code for the strings.Replace function

godoc

A simple static webserver for easier documentation browsing. I use it to preview how my documentation will look on godocs.io and pkg.go.dev.
godoc -http=:6060

Then just open your webbrowser to:
http://localhost:6060