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: export_test.go
    path of file: ./repos/juju/apiserver/facades/agent/metricsender
    
    the code of the file until where you have to start completion: // Copyright 2014 Canonical Ltd.  All rights reserved.
// Licensed under the AGPLv3, see LICENCE file for details.

package met
    
func PatchHost(host string) func() {
	restoreHost := testing.PatchValue(&defaultSenderFactory, func(url string) MetricSender {
		return &HTTPSender{url: host}
	})
	return func() {
		restoreHost()
	}
}