http://godoc.org/bitbucket.org/creachadair/stringset
The stringset package implements a lightweight set-of-strings type based around Go's built-in map type.
The stringset package is generated by the makeset program from source templates core.go.in (the main package source) and core_test.go.in (for the unit tests). To change the implementation, modify those templates and re-generate the package source by running:
go run ./makeset -config makeset/stringset.toml -output .