The Opaque API is the latest version of the Protocol Buffers implementation for the Go programming language. The old version is now called Open Struct API. See the Go Protobuf: Releasing the Opaque API blog post for an introduction. The migration to the Opaque API happens incrementally, on a per-proto-message or per-.proto-file basis, by setting the Protobuf Editions feature api_level option to one of its possible values: API_OPEN selects the Open Struct API; this was the only API before Dece...
