0 1 1 2 3 5 8 13 21 34 55 89 144 ...
-21 13 -8 5 －3 2 －1 1 0 1 1 2 3 5 8 13 21 ...

go get -v github.com/visualfc/fibutil

func fib.Fib(n int64) *big.Int
func fib.FastFib(n int64) *big.Int
func fib.FibList(n1, n2 int64) []string

fibutil n		:fibonacci number
fibutil n1 n2	:fibonacci number list

fibutil 10 		=> 55
fibutil -10 10  => [-55 34 -21 13 -8 5 -3 2 -1 1 0 1 1 2 3 5 8 13 21 34 55]
fibutil 299     => 137347080577163115432025771710279131845700275212767467264610201