Wrapping a ResponseWriter to capture the status code

example.go

// Create our own MyResponseWriter to wrap a standard http.ResponseWriter
// so we can store the status code.
type MyResponseWriter struct {
	status int 
	http.ResponseWriter
}

func NewMyResponseWriter(res http.ResponseWriter) *MyResponseWriter {
	// Default the status code to 200
	return &MyResponseWriter{200, res}
}

// Give a way to get the status
func (w MyResponseWriter) Status() int {
	return w.status
}

// Satisfy the http.ResponseWriter interface
func (w MyResponseWriter) Header() http.Header {
	return w.ResponseWriter.Header()
}

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

func (w MyResponseWriter) WriteHeader(statusCode int) {
	// Store the status code
	w.status = statusCode

	// Write the status code onward.
	w.ResponseWriter.WriteHeader(statusCode)
}

http.Pusher interface can be implemented, as the documentation states

// Push returns ErrNotSupported if the client has disabled push or if push
// is not supported on the underlying connection.

func (w *MyResponseWriter) Push(target string, opts *http.PushOptions) error {
	if p, ok := w.ResponseWriter.(http.Pusher); ok {
		return p.Push(target, opts)
	}
	return http.ErrNotSupported
}

http.Hijacker interface isn't implemented in http2 connections.