Go Implementation For Count of strings that can be formed using a, b and c under given constraints

This note is to add Go implementation of below problem
https://practice.geeksforgeeks.org/problems/count-of-strings-that-can-be-formed-using-a-b-and-c-under-given-constraints/0

Golang playground url :  https://play.golang.org/p/lkBcz2yE3f_k

Github code url