Go: How to parse only date to time.Time?

I want to parse only date value to time.Time.
For example I have date in this format: 2016-03-31, and I want to parse it, like: time.Parse(FORMAT, "2016-03-31").

But it always fail.

What is the correct format string to use to parse only date with this format?

I have the code below as example, it is on playground also: https://play.golang.org/p/0MNLr9emZd

package main

import (
	"fmt"
	"time"
)

var dateToParse = "2016-03-31"

func main() {
	format := "2006-12-01"
	parseDate(format)
}

func parseDate(format string) {
	t, err := time.Parse(format, dateToParse)
	if err != nil {
		fmt.Println("Format:", format)
		fmt.Println(err)
		fmt.Println("")
		return
	}
	fmt.Println("Works Format:", format)
	fmt.Println(t)
	fmt.Println("")
}

The output is this:

Format: 2006-12-01
parsing time "2016-03-31" as "2006-12-01": cannot parse "-31" as "2"

> Package time
>
> These are predefined layouts for use in Time.Format and Time.Parse.
> The reference time used in the layouts is the specific time:
>
> Mon Jan 2 15:04:05 MST 2006
>
> which is Unix time 1136239445. Since MST is GMT-0700, the reference
> time can be thought of as
>
> 01/02 03:04:05PM '06 -0700
>
> To define your own format, write down what the reference time would
> look like formatted your way; see the values of constants like ANSIC,
> StampMicro or Kitchen for examples.

Use format := "2006-01-02" for yyyy-mm-dd.

Per Go 1.20 release note

> The new time layout constants DateTime, DateOnly, and TimeOnly provide names for three of the most common layout strings used in a survey of public Go source code.

    DateTime   = "2006-01-02 15:04:05"
	DateOnly   = "2006-01-02"
	TimeOnly   = "15:04:05"

The new format DateOnly = "2006-01-02" of format.go will be added in the Go next release (1.20) per proposal time: add DateTime, DateOnly, TimeOnly format constants and commit

time.Parse(time.DateOnly, dateToParse)