func AuthMiddleware(c *mv.Context) {
log.Println("Simulate user authentication.")
rand.Seed(time.Now().Unix())
if rand.Int()%2 == 0 {
c.Response.Write([]byte("User authenticated.\n"))
c.Next()
} else {
c.Response.WriteHeader(http.StatusUnauthorized)
c.Response.Write([]byte("Use not authenticated.\n"))
c.Abort()
}
}