Wrapping json member fields to object

My objective is to add fields to json on user request.

Everything is great, but when displaying the fields with

fmt.Printf("%s: %s\n", content.Date, content.Description)

an error occurs:

invalid character '{' after top-level value

And that is because after adding new fields the file looks like this:

{"Date":"2017-03-20 10:46:48","Description":"new"}
{"Date":"2017-03-20 10:46:51","Description":"new .go"}

The biggest problem is with the writting to file

reminder := &Name{dateString[:19], text} //text - input string
newReminder, _ := json.Marshal(&reminder)

I dont really know how to do this properly

My question is how should I wrap all member fields into one object?
And what is the best way to iterate through member fields?

The code is available here: https://play.golang.org/p/NunV_B6sud

You should store the reminders into an array inside the json file, as mentioned by @Gerben Jacobs, and then, every time you want to add a new reminder to the array you need to read the full contents of rem.json, append the new reminder in Go, truncate the file, and write the new slice into the file. Here's a quick implentation https://play.golang.org/p/UKR91maQF2.

If you have lots of reminders and the process of reading, decoding, encoding, and writing the whole content becomes a pain you could open the file, implement a way to truncate only the last ] from the file contents, and then write only , + new reminder + ].

So after some research, people in the go-nuts group helped me and suggested me to use a streaming json parser that parses items individually.

So I needed to change my reminder listing function:

func listReminders() error {
	f, err := os.Open("rem.json")
	if err != nil {
		return err
	}
	dec := json.NewDecoder(f)
	for {
		var content Name
		switch dec.Decode(&content) {
		case nil:
			fmt.Printf("%#v\n", content)
		case io.EOF:
			return nil
		default:
			return err
		}
	}
}

Now everything works the way I wanted.