It's not an auth strategy but a mode without any authentication flow applied to the SPClient.
Anonymous mode can be handy in a situation when Gosip SharePoint-aware helpers intended to be used however authentication is handled by any other middleware.
Struct
Only SiteURL is required.
type AuthCnfg struct {
// SPSite or SPWeb URL, which is the context target for the API calls
SiteURL string `json:"siteUrl"`
}