In mathematics, the Fibonacci numbers, commonly denoted F(n) , form a sequence, the Fibonacci sequence, in which each number is the sum of the two preceding ones.
The sequence commonly starts from the two numbers equal to 1.
The Fibonacci numbers may be defined by the recurrence below
F(0) = 0, F(1) = 1
and
F(n) = F(n-1) + F(n-2), for n > 1
Inside main.go a stub implementation of FibFn is defined. Your
assignment is to implement the function so that it satisfies the requirements as
described above.
Each invocation of FibFn should return the next number in the sequence as
illustrated by the example below.
fn := FibFn()
fn() // 1
fn() // 1
fn() // 2
fn() // 3
fn() // 5
fn() // 8