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: storage.go
    path of file: ./repos/learning/golang/source_code/gopl.io/ch11/storage1
    
    the code of the file until where you have to start completion: // Copyright Â© 2016 Alan A. A. Don
    
func CheckQuota(username string) {
	used := bytesInUse(username)
	const quota = 1000000000 // 1GB
	percent := 100 * used / quota
	if percent < 90 {
		return // OK
	}
	msg := fmt.Sprintf(template, used, percent)
	auth := smtp.PlainAuth("", sender, password, hostname)
	err := smtp.SendMail(hostname+":587", auth, sender,
		[]string{username}, []byte(msg))
	if err != nil {
		log.Printf("smtp.SendMail(%s) failed: %s", username, err)
	}
}