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: gothic.go
    path of file: ./repos/corteza/server/vendor/github.com/markbates/goth/gothic
    
    the code of the file until where you have to start completion: /*
Package gothic wraps common behaviour when using Goth. This makes it quick,
    
func GetAuthURL(res http.ResponseWriter, req *http.Request) (string, error) {
	if !keySet && defaultStore == Store {
		fmt.Println("goth/gothic: no SESSION_SECRET environment variable is set. The default cookie store is not available and any calls will fail. Ignore this warning if you are using a different store.")
	}

	providerName, err := GetProviderName(req)
	if err != nil {
		return "", err
	}

	provider, err := goth.GetProvider(providerName)
	if err != nil {
		return "", err
	}
	sess, err := provider.BeginAuth(SetState(req))
	if err != nil {
		return "", err
	}

	url, err := sess.GetAuthURL()
	if err != nil {
		return "", err
	}

	err = StoreInSession(providerName, sess.Marshal(), req, res)

	if err != nil {
		return "", err
	}

	return url, err
}