code: func (b *BasicAuth) UnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
  	if err := b.doAuth(ctx); err != nil {
  		return nil, err
  	}
  	return handler(ctx, req)
  }
docs: // UnaryInterceptor define unary interceptor