Fibonacci is the sequence as follows:
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 …
The sequence can start with a zero or a one.
fib uses two ways to calculate fibonacci number, FibonacciLoop and FibonacciRecursion. There is another shortcut method Fib, which calls FibonacciLoop since FibonacciRecursion isn't always efficient.
fmt.Println(fib.Fib(5)) // 5