fix #692. cache not working when get err in queryConfig

[zxc111]

No description provided.

[CLAassistant]

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[binbin0325]

Why do need to set param

[zxc111]

https://github.com/nacos-group/nacos-sdk-go/blob/5fedf574d9d87221e51c1102423604a734698f0f/clients/config_client/config_client.go#L180C1-L180C1

func (client *ConfigClient) GetConfig(param vo.ConfigParam) (content string, err error) {
	content, err = client.getConfigInner(&param)
	if err != nil {
		return "", err
	}
	param.UsageType = vo.ResponseType
	if err = filter.GetDefaultConfigFilterChainManager().DoFilters(&param); err != nil {
		return "", err
	}
	content = param.Content
	return content, nil
}

GetConfig call client.getConfigInner(&param). GetConfigInner return content without err when failover or read from cache, and param.Content is set only in the normal process. if don't set param.Content, which content is returned by GetConfig will be empty when failover or cache :

	if response != nil && response.Response != nil && !response.IsSuccess() {
		return response.Content, errors.New(response.GetMessage())
	}
	param.EncryptedDataKey = response.EncryptedDataKey
	param.Content = response.Content
	return response.Content, nil

[binbin0325]

https://github.com/nacos-group/nacos-sdk-go/pull/668，there is a problem with the changes in this, and look at it after repair

[binbin0325]

Fixed: #697