This is little library to operate with bank holidays in Poland.

holidays := holidays_pl.New()

// to get list of all holidays
holidays.GetHolidaysList(d.Year())

// get holiday by date or false as second returned value
hh, ok := holidays.GetByDate(time.Date(2024, time.March, 31, 0, 0, 0, 0, time.UTC))

For more info just look at th tests file.