Hacking variadics to have optional arguments

variadic_opt.go

package main

import (
  "net/http"
  "encoding/json"
)

// Using variadic (hack) to default the response code to 200
func sendJSON(w http.ResponseWriter, v interface{}, status ...int) {
	st := http.StatusOK
	if len(status) > 0 {
		st = status[0]
	}

	w.Header().Add("Content-Type", "application/json")
	w.WriteHeader(st)
	if err := json.NewEncoder(w).Encode(v); err != nil {
		log.Errorf("Failed to send response: %s", err)
	}
}

func handler(w http.ResponseWriter, r *http.Request) {
  if true {
    sendJSON(w, "something went wrong", http.StatusInternatServerError)
  }
  sendJSON(w, "Hello world") // Returns 200
}