A Tour of Go Numeric Constants

Numeric constants are high-precision values.

An untyped constant takes the type needed by its context.

Try printing needInt(Big) too.

package main 

import "fmt"

const (
    Big = 1 << 100
    Small = Big >> 99
)

func needInt(x int) int {
    return x*10 + 1
}

func needFloat(x float64) float64{
    return x * 0.1
}

func main() {
    fmt.Println(needInt(Small))
    fmt.Println(needFloat(Small))
    fmt.Println(needFloat(Big))
}