Infinite and NaN

var z float64
fmt.Println(z, -z, 1/z, -1/z, z/z) // "0 -0 +Inf -Inf NaN"

NaN (‘‘not a number’’): the result of mathematically dubious operations as 0/0 or Sqrt(-1) .

The function math.IsNaN tests whether its argument is a not-a-number value, and math.NaN returns such a value.

NaN is always false

nan := math.NaN()
fmt.Println(nan == nan, nan < nan, nan > nan) // "false false false"

It's better to avoid NaN to test for failure and instead report the failure separately:

func compute() (value float64, ok bool) {
    // ...
    if failed {
        return 0, false
    }
    return result, true
}