code: func (grng GammaGenerator) Gamma(alpha, beta float64) float64 {
  	if !(alpha > 0.0) || !(beta > 0.0) {
  		panic(fmt.Sprintf("Invalid parameter alpha %.2f beta %.2f", alpha, beta))
  	}
  
  	return grng.gamma(alpha, beta)
  }
docs: // Gamma returns a random number of gamma distribution (alpha > 0.0 and beta > 0.0)