When does the newly created mysql username or password contain characters ? , the startup will fail.

[midy177]

When does the newly created mysql username or password contain characters ? , the startup will fail.

After inspection, it was found that in collector/exporter.go:107After inspection, it was found that in the processing method of collector/exporter.go 107, when the password contains the characters ? The logic does not work correctly.
```golang`
// New returns a new MySQL exporter for the provided DSN.
func New(ctx context.Context, dsn string, scrapers []Scraper, logger log.Logger) *Exporter {
// Setup extra params for the DSN, default to having a lock timeout.
dsnParams := []string{fmt.Sprintf(timeoutParam, *exporterLockTimeout)}

if *slowLogFilter {
	dsnParams = append(dsnParams, sessionSettingsParam)
}

if strings.Contains(dsn, "?") {
	dsn = dsn + "&"
} else {
	dsn = dsn + "?"
}
dsn += strings.Join(dsnParams, "&")

return &Exporter{
	ctx:      ctx,
	logger:   logger,
	dsn:      dsn,
	scrapers: scrapers,
}

}

 It is recommended to change it to:
```golang
// New returns a new MySQL exporter for the provided DSN.
func New(ctx context.Context, dsn string, scrapers []Scraper, logger log.Logger) *Exporter {
	// Setup extra params for the DSN, default to having a lock timeout.
	dsnParams := []string{fmt.Sprintf(timeoutParam, *exporterLockTimeout)}

	if *slowLogFilter {
		dsnParams = append(dsnParams, sessionSettingsParam)
	}

	if !strings.HasSuffix(dsn, ")/") {
		arr := strings.Split(dsn, ")/")
		lastItem := arr[len(arr)-1]
		if strings.Contains(lastItem, "?") {
			dsn = dsn + "&"
		}
	} else {
		dsn = dsn + "?"
	}
	dsn += strings.Join(dsnParams, "&")

	return &Exporter{
		ctx:      ctx,
		logger:   logger,
		dsn:      dsn,
		scrapers: scrapers,
	}
}