In Go Lang Set the Tag for a Whole Struct

I'm using Go and GoRestful to program a RESTFUL front end to some entities stored on Google App Engine Datastore.

The data is turned into JSON/XML and presented to the user with tags controlling the style for each format. How can I also apply tags to the name of the struct itself so it is output using the correct style?

An example of my structs would be:

type Shallow struct {
	Key          string    `datastore:"-" json:"key" xml:"key"`
	LastModified time.Time `json:"last_modified" xml:"last-modified"`
	Version      int       `json:"version" xml:"version"`
	Status       int       `json:"status" xml:"status"`
	Link         Link      `datastore:"-" json:"link" xml:"link"`
	Name         string    `json:"name" xml:"name"`
}

type ProbabilityEntry struct {
	ItemId      int64   `datastore:"ItemId" json:"item_id" xml:"item-id"`
	Probability float32 `datastore:"Probability" json:"probability" xml:"probability"`
	Quantity    int16   `datastore:"Quantity" json:"quantity" xml:"quantity"`
}

type LootTable struct {
	Shallow
	AllowPreload  bool               `json:"allow_preload" xml:"allow-preload"`
	Probabilities []ProbabilityEntry `json:"probabilities" xml:"probabilities"`
}

When the LootTable struct emits to JSON/XML it should represent itself as 'loot_table' or 'loot-table' rather than 'LootTable'.

Simple answer:

Wrap it in an outer struct:

type Payload struct {
   Loot LootTable `json:"loot_table"`
}

Longer answer:

If the receiver of the JSON knows what they're getting then this is not really necessary. However, when building a JSON API I often create a Response struct that contains extra details regarding the request, that could include the type of the response. Here is an example:

type JSONResponse struct {
   Obj    interface{} `json:"obj"`    // Marshall'ed JSON (not wrapped)
   Type   string      `json:"type"`   // "loot_table" for example
   Ok     bool        `json:"ok"`     // Does this response require error handling?
   Errors []string    `json:"errors"` // Any errors, you could leave out Ok and just check this
}

Again, with API calls you usually know what you're expecting, but if the response could be one of a number of types this approach can help.