Golang - HTTP Server - Contexts

main.go

package main

import (
	"fmt"
	"github.com/julienschmidt/httprouter"
	"log"
	"net/http"
	"os"
	"strconv"
)

type appContext struct {
	someBool bool
	params   *httprouter.Params
	session  *sessionContext
}

type sessionContext struct {
	userID int64
}

type appHandle func(http.ResponseWriter, *http.Request, *appContext) (int, error)

func RouteWithContext(c *appContext, handle appHandle) httprouter.Handle {
	return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
		log.Println("AppHandler anon func")

		c.params = &p
		c.session = &sessionContext{}
		c.session.userID = 5

		status, err := handle(w, r, c)

		if err != nil {
			log.Printf("HTTP %d: %q", status, err)
			http.Error(w, http.StatusText(status), status)
			return
		}

	}
}

func NewAppContext() *appContext {
	return &appContext{someBool: true}
}

func main() {
	// log to stdout (the default is stderr).
	log.SetOutput(os.Stdout)
	log.Println("*** running")

	context := NewAppContext()

	// wire routes to handlers
	router := httprouter.New()
	router.GET("/", RouteWithContext(context, IndexHandler))
	router.GET("/set/:id", RouteWithContext(context, SetHandler))

	// listen and serve
	err := http.ListenAndServe(":8080", router)
	if err != nil {
		log.Fatal(err)
	}
}

func IndexHandler(w http.ResponseWriter, r *http.Request, c *appContext) (int, error) {
	log.Println("IndexHandler")

	fmt.Fprintln(w, "IndexHandler")
	fmt.Fprintf(w, "  - userID   = %d\n", c.session.userID)
	fmt.Fprintf(w, "  - someBool = %t\n", c.someBool)

	return 200, nil
}

func SetHandler(w http.ResponseWriter, r *http.Request, c *appContext) (int, error) {
	log.Println("SetHandler")
	id, err := strconv.ParseInt(c.params.ByName("id"), 10, 0)
	if err != nil {
		return 500, err
	}

	c.session.userID = id

	http.Redirect(w, r, "/", http.StatusSeeOther)
	return http.StatusSeeOther, nil
}