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: util.go
    path of file: ./repos/prometheus/discovery
    
    the code of the file until where you have to start completion: // Copyright 2020 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under t
    
func (rh *metricRegistererImpl) RegisterMetrics() error {
	for _, collector := range rh.metrics {
		err := rh.reg.Register(collector)
		if err != nil {
			// Unregister all metrics that were registered so far.
			// This is so that if RegisterMetrics() gets called again,
			// there will not be an error due to a duplicate registration.
			rh.UnregisterMetrics()

			return fmt.Errorf("failed to register metric: %w", err)
		}
	}
	return nil
}