Report the payload size when erroring

Author: Luis Fonseca

Diff for: client_test.go

@@ -516,8 +516,7 @@ func TestDataSizeValidation(t *testing.T) {
 	data := strings.Repeat("a", 20481)
 	err := client.Trigger("channel", "event", data)
 
-	assert.EqualError(t, err, "Event payload exceeded maximum size")
-
+	assert.EqualError(t, err, "Event payload exceeded maximum size (20481 bytes is too much)")
 }
 
 func TestInitialisationFromURL(t *testing.T) {

Diff for: encoder.go

@@ -38,7 +38,7 @@ func encodeTriggerBody(channels []string, event string, data interface{}, socket
 		payloadData = string(dataBytes)
 	}
 	if len(payloadData) > maxEventPayloadSize {
-		return nil, errors.New("Event payload exceeded maximum size")
+		return nil, errors.New(fmt.Sprintf("Event payload exceeded maximum size (%d bytes is too much)", len(payloadData)))
 	}
 	return json.Marshal(&eventPayload{
 		Name:     event,