You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: server.go
    path of file: ./repos/open-match/tutorials/custom_evaluator/evaluator/evaluate
    
    the code of the file until where you have to start completion: // Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.

    
func (s *EvaluatorService) Evaluate(stream pb.Evaluator_EvaluateServer) error {
	var proposals = []*pb.Match{}
	for {
		req, err := stream.Recv()
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		proposals = append(proposals, req.GetMatch())
	}

	logger.WithFields(logrus.Fields{
		"proposals": proposals,
	}).Trace("proposals received by the evaluator")

	results, err := evaluate(proposals)
	if err != nil {
		return status.Error(codes.Aborted, err.Error())
	}

	for _, result := range results {
		if err := stream.Send(&pb.EvaluateResponse{MatchId: result}); err != nil {
			return err
		}
	}

	logger.WithFields(logrus.Fields{
		"results": results,
	}).Trace("matches accepted by the evaluator")
	return nil
}