Possible overflow in r1csqap/LagrangeInterpolation

[ShuangWu121]

The function "NewPolZeroAt" in r1csqap.go, which is used by function "LagrangeInterpolation"

has the following code

fac := 1
	for i := 1; i < totalPoints+1; i++ {
		if i != pointPos {
			fac = fac * (pointPos - i)
		}
	}
facBig := big.NewInt(int64(fac))

I am facing a problem that 'fac' can be larger than int64, which make the algorithm generate wrong polynomial. Has anyone else faced this problem as well?