• PR #235 adds the ability to use Go 13+ standard library methods errors.Is and errors.As to unwrap errors from Twirp's internal errors. This works for service errors, usually unwrapped on middleware, and also client errors if they fail on the client, for example a context cancelled error. NOTE: client errors can only be unwrapped if the client was generated with Twirp v5.11.0 or above (even if your service is using a different Twirp version). For older versions, you can still use (github.com/pkg/errors).Unwrap.
• PR #227 adds the helper function AddHTTPResponseHeader, that can be used to set multiple values to the response header in the same key.