Ninja Level 3 Hands on Exercise #2

main.go

package main

import (
	"context"
	"fmt"
	"time"

	"github.com/mannion007/whatever/session"
)

func main() {
	ctx := context.Background()

	ctx, cancel := context.WithTimeout(ctx, time.Second)
	defer cancel()

	ctx = session.WithUserID(ctx, 500)
	ctx = session.WithUserIP(ctx, "127.0.0.1")

	fmt.Println(*session.UserIDFrom(ctx))
	fmt.Println(*session.UserIPFrom(ctx))
}

session.go

package session

import "context"

type userIDKey int
type userIPKey int

var userID userIDKey = 0
var userIP userIPKey = 1

// WithUserID decorates the supplied context with the supplied User ID
func WithUserID(ctx context.Context, id int) context.Context {
	return context.WithValue(ctx, userID, id)
}

// WithUserIP decorates the supplied context with the supplied User IP
func WithUserIP(ctx context.Context, ip string) context.Context {
	return context.WithValue(ctx, userIP, ip)
}

// UserIDFrom extracts the User ID from the supplied context
func UserIDFrom(ctx context.Context) *int {
	value, ok := ctx.Value(userID).(int)

	if !ok {
		return nil
	}

	return &value
}

// UserIPFrom extracts the User IP from the supplied context
func UserIPFrom(ctx context.Context) *string {
	value, ok := ctx.Value(userIP).(string)

	if !ok {
		return nil
	}

	return &value
}