Golang Chi router not rendering response payload JSON - json

Question

Go here using Chi renderer for a basic REST service. I have the following structs and functions:
type Order struct {
OrderId uuid.UUID `json:"orderId",gorm:"type:uuid;primary_key;not null;default gen_random_uuid()"`
Quantity int `json:"quantity",gorm:"not null"`
Status string `json:"status",gorm:"not null"`
}
func (o *Order) Bind(r *http.Request) error {
return nil
}
func (o *Order) Render(w http.ResponseWriter, r *http.Request) error {
return nil
}
func NewOrdersList(orders []Order) []render.Renderer {
list := []render.Renderer{}
for _, order := range orders {
list = append(list, &order)
}
return list
}
func GetOrderByIdHandler() http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
orderId := chi.URLParam(r, "orderId")
order, err := fetchOrder(orderId)
if err != nil {
render.Render(w, r, NewInternalServerError(err))
return
}
log.Info("order status is " + order.Status)
render.Bind(r, &order)
return
}
}
When I run this and hit the endpoint that invokes the GetOrderByIdHandler() function, I get back a 200 OK/Success. However there is no JSON in the response body, whereas I would have expected a marshalled JSON payload representing an "order", such as:
{
"orderId": "12345",
"quantity": 1,
"status": "SENT"
}
However my curl shows nothing in the response body:
$ curl -i -H "Content-Type: application/json" -H "Accept: application/json" -X GET http://localhost:9400/myapp/v1/orders/12345
HTTP/1.1 200 OK
Vary: Origin
Date: Wed, 24 Jun 2020 07:09:30 GMT
Content-Length: 0
Any idea where I'm going awry? I do see the log statement print out the order status right before calling bind, so I know its not a null/empty order instance.

Answer 1

render.Bind is input-only, i.e. for decoding the request payload. Instead use render.JSON to send a json response.
func GetOrderByIdHandler() http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
orderId := chi.URLParam(r, "orderId")
order, err := fetchOrder(orderId)
if err != nil {
render.Render(w, r, NewInternalServerError(err))
return
}
log.Info("order status is " + order.Status)
render.JSON(w, r, order)
}
}
Or, alternatively, you could also use the standard approach: import the encoding/json package and then use it like so:
func GetOrderByIdHandler() http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
orderId := chi.URLParam(r, "orderId")
order, err := fetchOrder(orderId)
if err != nil {
render.Render(w, r, NewInternalServerError(err))
return
}
log.Info("order status is " + order.Status)
w.Header().Set("Content-Type", "application/json")
if err := json.NewEncoder(w).Encode(order); err != nil {
render.Render(w, r, NewInternalServerError(err))
}
}
}
Also note that the proper format for multiple struct tags is "space delimited" not "comma separated". For example: json:"quantity" gorm:"not null" is correct, while json:"quantity",gorm:"not null" is not.