Currently is legacy but was a popular way of exposing SharePoint into external world back in the days.
Struct
type AuthCnfg struct {
// SPSite or SPWeb URL, which is the context target for the API calls
SiteURL string `json:"siteUrl"`
// Username for SharePoint On-Prem,
// format depends in TMG settings, can include domain or doesn't
Username string `json:"username"`
// User password
Password string `json:"password"`
}