Fibonacci implementation using closures in Go

fib_closure.go

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
    seqIndex := -1
    lastFib := 0
    beforeLastFib := 0
    
    return func() int {
        seqIndex += 1
        
        if seqIndex == 0 {
          lastFib = 0
        } else if seqIndex == 1 {
          lastFib = 1
        } else {
          newFib := lastFib + beforeLastFib //fib(n) = fib(n - 1) + fib(n - 2)
          beforeLastFib = lastFib
          lastFib = newFib
        }
        return lastFib
    }
}

func main() {
    f := fibonacci()
    for i := 0; i < 10; i++ {
        fmt.Println(f())
    }
}