How one can Discover the Final Fibonacci Digit in Golang

The problem

Return the final digit of the nth factor within the Fibonacci sequence (beginning with 1,1, to be further clear, not with 0,1 or different numbers).

LastFibDigit(1) == 1
LastFibDigit(2) == 1
LastFibDigit(3) == 2
LastFibDigit(1000) == 5
LastFibDigit(1000000) == 5

The answer in Golang

Possibility 1:

bundle resolution
func LastFibDigit(n int) int {
  n %= 60
  a, b := 0, 1
  for i := 0; i<n; i++ { a, b = b, a+b }
  return a % 10
}

Possibility 2:

bundle resolution
func LastFibDigit(n int) int {
  fib := []int{0, 1}
  for i := 1; i < 60; i++ {
    fib = append(fib, (fib[i]+fib[i-1])%10)
  }
  j := n % 60
  return fib[j]
}

Possibility 3:

bundle resolution
import "math"
func LastFibDigit(n int) int {
  return int(math.Pow(math.Phi, float64(npercent60))/math.Sqrt(5) + 0.5) % 10
}

Take a look at instances to validate our resolution

bundle solution_test
import (
  . "github.com/onsi/ginkgo"
  . "github.com/onsi/gomega"
)
var _ = Describe("Pattern check instances", func() {
  It("Primary checks", func() {
    Anticipate(LastFibDigit(1)).To(Equal(1))
    Anticipate(LastFibDigit(21)).To(Equal(6))
    Anticipate(LastFibDigit(302)).To(Equal(1))
    Anticipate(LastFibDigit(4003)).To(Equal(7))
    Anticipate(LastFibDigit(50004)).To(Equal(8))
    Anticipate(LastFibDigit(600005)).To(Equal(5))
    Anticipate(LastFibDigit(7000006)).To(Equal(3))
    Anticipate(LastFibDigit(80000007)).To(Equal(8))
    Anticipate(LastFibDigit(900000008)).To(Equal(1))
    Anticipate(LastFibDigit(1000000009)).To(Equal(9))
  })
})