Go Time Duration Integers

I've been programming in Go for years now, and I released figtree to solve this duration type of a problem for me, but sometimes, you don't need or can't use figtree. That's okay too. What I have noticed is that if you use flag.Duration you need to pass the nanosecond value as an int into the flag in order for it to actually work.

For example, if you have a flag.Duration called -timeout set to a default of 5 * time.Minute then its int value is 300000000000 which is 300_000_000_000 (300B). If you use -timeout 5 for the flag, you're going to be off by 299,999,999,995 ns.

This simple Go program prints these various nanosecond integers needed for common human readable durations.

func main() {
    fmt.Println("| Human Time | `int` Value | Go Syntax |")
    fmt.Println("|------------|-------------|---------------|")
    for i := range over(1, 60, 5) {
        fmt.Printf("| `%d%s` | `%d` | `%d * time.Second` |\n", int(i), "s", i*time.Second, i)
    }
    for i := range over(1, 60, 5) {
        fmt.Printf("| `%d%s` | `%d` | `%d * time.Minute` |\n", int(i), "m", i*time.Minute, i)
    }
    for i := range over(1, 24, 1) {
        fmt.Printf("| `%d%s` | `%d` | `%d * time.Hour` |\n", int(i), "h", i*time.Hour, i)
    }
}

I want to point your attention to the over() func because it's traditionally not accessible in languages like Go. However, a custom interator was built for this stepping output.

func over(start, stop, step int) iter.Seq[time.Duration] {
    return func(yield func(time.Duration) bool) {
        if start <= stop {
            if !yield(time.Duration(start)) {
                return
            }
        }

        firstMultiple := start + (step - start%step)
        if start%step == 0 {
            firstMultiple = start + step
        }

        for i := firstMultiple; i <= stop; i += step {
            if !yield(time.Duration(i)) {
                return
            }
        }
    }
}

When executed this program generates the following markdown table.

Human Time	int Value	Go Syntax
1s	1000000000	1 * time.Second
5s	5000000000	5 * time.Second
10s	10000000000	10 * time.Second
15s	15000000000	15 * time.Second
20s	20000000000	20 * time.Second
25s	25000000000	25 * time.Second
30s	30000000000	30 * time.Second
35s	35000000000	35 * time.Second
40s	40000000000	40 * time.Second
45s	45000000000	45 * time.Second
50s	50000000000	50 * time.Second
55s	55000000000	55 * time.Second
60s	60000000000	60 * time.Second
1m	60000000000	1 * time.Minute
5m	300000000000	5 * time.Minute
10m	600000000000	10 * time.Minute
15m	900000000000	15 * time.Minute
20m	1200000000000	20 * time.Minute
25m	1500000000000	25 * time.Minute
30m	1800000000000	30 * time.Minute
35m	2100000000000	35 * time.Minute
40m	2400000000000	40 * time.Minute
45m	2700000000000	45 * time.Minute
50m	3000000000000	50 * time.Minute
55m	3300000000000	55 * time.Minute
60m	3600000000000	60 * time.Minute
1h	3600000000000	1 * time.Hour
2h	7200000000000	2 * time.Hour
3h	10800000000000	3 * time.Hour
4h	14400000000000	4 * time.Hour
5h	18000000000000	5 * time.Hour
6h	21600000000000	6 * time.Hour
7h	25200000000000	7 * time.Hour
8h	28800000000000	8 * time.Hour
9h	32400000000000	9 * time.Hour
10h	36000000000000	10 * time.Hour
11h	39600000000000	11 * time.Hour
12h	43200000000000	12 * time.Hour
13h	46800000000000	13 * time.Hour
14h	50400000000000	14 * time.Hour
15h	54000000000000	15 * time.Hour
16h	57600000000000	16 * time.Hour
17h	61200000000000	17 * time.Hour
18h	64800000000000	18 * time.Hour
19h	68400000000000	19 * time.Hour
20h	72000000000000	20 * time.Hour
21h	75600000000000	21 * time.Hour
22h	79200000000000	22 * time.Hour
23h	82800000000000	23 * time.Hour
24h	86400000000000	24 * time.Hour

🔖 Bookmark this page. It'll come in handy later for you. It's just 60B nanoseconds per minute. So you have 60 and 000000000 after aka 000_000_000. So 9 zeros after your second count. 17 seconds plus 9 zeros is 17_000_000_000 is 17 * time.Second.

I suppose that after writing this blog post about this I'll always remember that time.Duration is 9 zeros after the quantity of seconds. If you miss those 9 zeros, your duration will appear instant.