package main

import (
    "fmt"
    "math"
)

func main() {
    var pagesize int = 10
    var length  int = 43

    d := float64(length / pagesize)
    page := int(math.Ceil(d))

    fmt.Println(page)
    // output 4 not 5
}

d := float64(length / pagesize)

d := float64(length) / float64(pagesize)

d := float64(length) / float64(pagesize)

page := length / pagesize
if length % pagesize > 0 {
    page++
}