Golang function to return a "simple number"

main.go

package main

import (
	"fmt"
	"math"
)

func main() {
	fmt.Println(NumberFormat(123))
	fmt.Println(NumberFormat(12345))
	fmt.Println(NumberFormat(12345678))
	fmt.Println(NumberFormat(1234567890123))
	fmt.Println(NumberFormat(1234567890123456))
	fmt.Println(NumberFormat(1234567890123456789))
}

func NumberFormat(num float64) string {
	// Inspired by https://stackoverflow.com/a/66105942
	units := [5]string{"k", "M", "B", "T", "Q"}

	unit := len(fmt.Sprintf("%.0f", math.Floor(num/1.0e+1)))

	x := math.Abs(num) / math.Pow(10, float64(unit-(unit%3)))
	i := int(math.Floor(float64(unit)/3.0) - 1.0)

	if i < 0 || i > len(units)-1 {
		return fmt.Sprintf("%.0f", num)
	}
	return fmt.Sprintf("%.2f%s", x, units[i])
}

output.txt

]$ go run .
123
12.35k
12.35M
1.23T
1.23Q
1234567890123456768