code: func (adapter *Decoder) UseNumber() {
  	cfg := adapter.iter.cfg.configBeforeFrozen
  	cfg.UseNumber = true
  	adapter.iter.cfg = cfg.frozeWithCacheReuse(adapter.iter.cfg.extraExtensions)
  }
docs: // UseNumber causes the Decoder to unmarshal a number into an interface{} as a
  // Number instead of as a float64.