code: func (j *Json) MustFloat64(args ...float64) float64 {
  	var def float64
  
  	switch len(args) {
  	case 0:
  	case 1:
  		def = args[0]
  	default:
  		log.Panicf("MustFloat64() received too many arguments %d", len(args))
  	}
  
  	f, err := j.Float64()
  	if err == nil {
  		return f
  	}
  
  	return def
  }
docs: // MustFloat64 guarantees the return of a `float64` (with optional default)
  //
  // useful when you explicitly want a `float64` in a single value return context:
  //     myFunc(js.Get("param1").MustFloat64(), js.Get("optional_param").MustFloat64(5.150))