Order dates chronologically in Go

Recently I had to order an array of structures based on a time.Time field. Doing this was surprisingly easy in Go, so much that it is worth a small post :-)
Imagine you have a structure that contains a Date field, let’s use a simple Post structure as an example:

type Post struct {
    Id       int64
    Date     time.Time
    Title    string
    Content  string
}

There is a chance that you will also have a container for those Posts in your code.

posts := []Post{p1, p2, p3, p4}

Now, how can you sort this array by dates? If you search for sort array in Go you will get as first result the sort package with some great examples. Sorting by a time.Time type is not different, all you need is to change the sort implementation for Time type.
So for this specific example we need to implement Len, Swap and Less. For the Less function, use the Before function available in the time package.

type ByDate []Post

func (a ByDate) Len() int           { return len(a) }
func (a ByDate) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByDate) Less(i, j int) bool { return a[i].Date.Before(a[j].Date) }

Finally, just call the sort function:

sort.Sort(ByDate(posts))

I made a Gist sortbydate.go with a simple example, an array of dates, and as you can see this is easily extendable.