Hey,

The `json.Unmarshal` func will do the type casting and with package `reflect`, and return an error if the JSON is not valid:

http://golang.org/src/pkg/encoding/json/decode.go?s=2221:2269#L127

So using `[]string` is the right way to do in Go.  Also, anyhow if you keep the `interface{}`, at some point you'll have to cast it to a `string`, which you do in `brog` in a `if` statement without doing a type check, which would result in a panic if the post header was malformed, and eventually `panic` the goroutine that's serving that post.  That would effectively crash the whole website.

Instead, you use a `string` and let the decoder fail if the type check doesn't match, and then `brog` will simply reject the post as malformed and print a message in the console, so the user can fix their post header.