code: func (mt *MT19937) Seed(seed int64) {
  	x := mt.state
  	x[0] = uint64(seed)
  	for i := uint64(1); i < n; i++ {
  		x[i] = 6364136223846793005*(x[i-1]^(x[i-1]>>62)) + i
  	}
  	mt.index = n
  }
docs: // Seed uses the given 64bit value to initialise the generator state.
  // This method is part of the rand.Source interface.