respond

type Encoder interface {
	// Encode writes a serialization of v to w, optionally using additional
	// information from the http.Request to do so.
	Encode(w http.ResponseWriter, r *http.Request, v interface{}) error
	// ContentType gets a string that will become the Content-Type header
	// when responding through w to the specified http.Request.
	// Most of the time the argument will be ignored, but occasionally
	// details in the request, or even in the headers in the ResponseWriter may
	// change the content type.
	ContentType(w http.ResponseWriter, r *http.Request) string
}

type Options struct {
	// AllowMultiple indicates that multiple responses are allowed. Otherwise,
	// multiple calls to With will panic.
	AllowMultiple bool

	// OnErr is a function field that gets called when an
	// error occurs while responding.
	// By default, the error panic but you may
	// use Options.OnErrLog to just log the error out instead,
	// or provide your own.
	OnErr func(err error)

	// Encoder is a function field that gets the encoder to
	// use to respond to the specified http.Request.
	// If nil, JSON will be used.
	Encoder func(w http.ResponseWriter, r *http.Request) Encoder

	// Before is called for before each response is written
	// and gives user code the chance to mutate the status or data.
	// Useful for handling different types of data differently (like errors),
	// enveloping the response, setting common HTTP headers etc.
	Before func(w http.ResponseWriter, r *http.Request, status int, data interface{}) (int, interface{})

	// After is called after each response.
	// Useful for logging activity after a response has been written.
	After func(w http.ResponseWriter, r *http.Request, status int, data interface{})

	// StatusData is a function field that gets the data to respond with when
	// WithStatus is called.
	// By default, the function will return an object that looks like this:
	//     {"status":"Not Found","code":404}
	StatusData func(w http.ResponseWriter, r *http.Request, status int) interface{}
}