template/scratch.go
func (s *Scratch) MapSet(k, mk string, v interface{}) (string, error) {
	s.init()

	s.Lock()
	defer s.Unlock()
	return s.mapSet(k, mk, v, true)
}
func (s *Scratch) MapSet(k, mk string, v interface{}) (string, error) {
	s.init()

	s.Lock()
	defer s.Unlock()
	return s.mapSet(k, mk, v, true)
}
// MapSet stores the value v into a key mk in the map named k.