Custom ResponseWriter

basic.go

type MyResponseWriter struct {
  http.ResponseWriter
}

func (m MyResponseWriter) Header() Header {
  return m.ResponseWriter.Header()
}

func (m MyResponseWriter) Write(d []byte) (int, error) {
  return m.ResponseWriter.Write(d)
}

func (m MyResponseWriter) WriteHeader(statusCode int) {
  m.ResponseWriter.WriteHeader(statusCode)
}

// And then you can do:
func (g *Gottp) ServeHTTP(res http.ResponseWriter, req *http.Request) {
  myWriter := MyResponseWriter(w)
  // and then go about your business as usual but using `myWriter instead of w`
}

notsobasic.go

type MyLoggingResponseWriter struct {
  http.ResponseWriter
  
  Status int
  Len int
}

func (m *MyLoggingResponseWriter) Header() Header {
  return m.ResponseWriter.Header()
}

func (m *MyLoggingResponseWriter) Write(d []byte) (int, error) {
  n, err := m.ResponseWriter.Write(d)
  m.Len = n
  return n, err
}

func (m *MyLoggingResponseWriter) WriteHeader(statusCode int) {
  m.Status = statusCode
  m.ResponseWriter.WriteHeader(statusCode)
}

// And then you can do:
func (g *Gottp) ServeHTTP(res http.ResponseWriter, req *http.Request) {
  myWriter := &MyResponseWriter(w)
  // So now after you write a response to the writer, you can log the content-size and the status.
  // In this scenario it's not that useful as you could get `n` from `n, err := myWriter.Write()` but I
  // usually use this write my logging middleware.
  myWriter.Write([]byte("hello"))
  log.Printf("The response was %d bytes long and the status was %d (%s)", myWriter.Len, myWriter.Status, http.StatusText(myWriter.Status))
}