Skellam PMF function in Go.
Uses a modified Bessel function of the first kind, Iα to calculate the probability mass function of the Skellam distribution.
However it uses a fork of components taken from https://github.com/dreading/gospecfunc which appear to be machine translations of GNU Octave components which don't work for the cases I care about. Within the ./amos directory are the files I've modified to work, primarily by initialising some float64 slices that are required for some cases.