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Redis – Struggling with the Go time module

I’m working with go-redis and trying to put a expiration on a Set I’m doing.

The examples in the documentation show –

func ExampleClient_Set() {
    // Last argument is expiration. Zero means the key has no
    // expiration time.
    err := rdb.Set("key", "value", 0).Err()
    if err != nil {
        panic(err)
    }

    // key2 will expire in an hour.
    err = rdb.Set("key2", "value", time.Hour).Err()
    if err != nil {
        panic(err)
    }
}

From what I can gather from the time documentation though (https://golang.org/pkg/time/), time.Hour should return “Hour returns the hour within the day specified by t, in the range [0, 23].”, which would make the expiration value different depending on what time of the day this code was run … I’m sure that’s not what they were going for, and as I’m sure the person who wrote the module knows Go better than me, I can’t imagine that’s what it actually does.

Being quite stumped, I read the go-redis code for Set (https://github.com/go-redis/redis/blob/0658532833205c238a41687728cb13c294504162/commands.go#L839) and it looked like it wanted seconds, unless you had something set, then it would want msecs, so I passed it 120 and it took a crap on first run saying “You’ve asked for 120ns, but the minimum is 1ms” … I added a pile of zeros and it expired almost as soon as I did my Set, so I finally gave up and just decided to ask for some help to do it properly instead of adding a bunch of zeros to every value I want and hoping it worked right.

I’ve got time.Minute in there now – based on the example I assume that’s giving me a minute, but I actually want two, and I have no idea after reading all this and trying all these things how to achieve that. Help would be GREATLY appreciated!!

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3

Answers


  1. 0

    From what I can gather from the time documentation though (https://golang.org/pkg/time/), time.Hour should return “Hour returns the hour within the day specified by t, in the range [0, 23].”

    You’re looking at the documentation for time.Time.Hour, which you’d use like this:

    now := time.Now()
fmt.Println(now.Hour())

    The documentation you’re looking for is of the constant time.Hour, which is a time.Duration defined as 60 * Minute – which happens to show you how to get the two minutes you’re looking for.

    2 * time.Minute
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  2. 0

    You’re confusing time.Hour with Time.Hour().

    time.Hour is a constant, that represents a duration of one hour. That’s what the code in your example uses.

    Time.Hour() is is a method on a time.Time value, which returns the hour within the day specified, as you quoted from documentation.

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  3. 0

    What the Set API needs is time.Duration type. If you need two minutes, use:

    err := rdb.Set("key", "value", 2*time.Minute).Err()

    You’re looking at the documentation for Time.Hour(), not time.Hour.

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