code: func UnaryServerInterceptor(opts ...Option) grpc.UnaryServerInterceptor {
  	o := evaluateOptions(opts)
  	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
  		if o.filterOutFunc != nil && !o.filterOutFunc(ctx, info.FullMethod) {
  			return handler(ctx, req)
  		}
  		newCtx, serverSpan := newServerSpanFromInbound(ctx, o.tracer, info.FullMethod)
  		resp, err := handler(newCtx, req)
  		finishServerSpan(ctx, serverSpan, err)
  		return resp, err
  	}
  }
docs: // UnaryServerInterceptor returns a new unary server interceptor for OpenTracing.