go generate is only useful if you have tools to use it with! Here is an incomplete list of useful tools that generate code.

• go tool yacc – Yacc for Go.
• stringer – Implements fmt.Stringer interface for enums.
• jsonenums – Implements json.Marshaler and json.Unmarshaler interfaces for enums.
• gen-mocks – Generate mocks for interfaces. Used in go-sourcegraph.