context Example

context_example.go

// Default HTTP handler
type Handler func(ctx *Context, w http.ResponseWriter, r *http.Request) error

// ServeHTTP implements http.Handler for our custom type Handler
func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ctx = NewContext(r)
	defer ctx.Cancel()

	err := h(ctx, w, r)

	code := http.StatusOK
	switch err {
	case nil:
		return
	case services.ErrNotAuthorized:
		code = http.StatusUnauthorized
	case services.ErrConflict:
		code = http.StatusConflict
	default:
		code = http.StatusInternalServerError
	}

	renderError(w, code, err)
	}
	
// Context is our context implementation
type Context struct {
	context.Context
  uuid       uuid.UUID
	logger     *log.Logger
	cancelFunc context.CancelFunc
}

//  inspired from https://github.com/golang/appengine/blob/master/appengine.go
func NewContext(req *http.Request) *Context {

	ctx, cancel = context.WithTimeout(context.Background(), DefaultHandlerTimeout)
	u := uuid.NewV4()
	logger := log.New(os.Stderr, u.String()+": ", logFlags)
	return &Context{
		Context:    ctx,
		uuid:       u,
		logger:     logger,
		cancelFunc: cancel,
	}
}

func (ctx *Context) Cancel() {
	ctx.cancelFunc()
}