How to format a date-time to display the timezone in IANA format?

The following code

fmt.Println(time.Now().Format("2 Jan 2006 03:04:05PM MST"))

prints

26 Nov 2021 04:00:31PM GMT

How to format the timezone as Europe/London i.e. in the IANA format? The expected output is

26 Nov 2021 04:00:31PM Europe/London

There isn't an option to do this directly with the time format layout.

However Location.String will print the IANA name in most cases.

> String returns a descriptive name for the time zone information, corresponding to the name argument to LoadLocation or FixedZone.

And LoadLocation usually takes the IANA string as input:

> If the name is "" or "UTC", LoadLocation returns UTC. If the name is "Local", LoadLocation returns Local.
>
> Otherwise, the name is taken to be a location name corresponding to a file in the IANA Time Zone database, such as "America/New_York".

Now "Local" isn't a valid IANA name, but "UTC" is — well, actually UTC is an alias of Etc/UTC.

The other gotcha with the std time package is that Location.String will print the name passed to FixedZone, and that can be literally anything.

So, if you are able to make assumptions about how your time.Location are instantiated, the following might be a viable solution:

fmt.Printf("%s %s", t.Format("2 Jan 2006 03:04:05PM"), t.Location())

Otherwise you will have to use some third-party package, or roll out your own mapping.