为什么我的随机数不更新？

I am doing the following in Golang (hosted on Appengine)

Whenever I initiate the app by running dev_appserver command and I access the page at localhost:8080, I get a page with a new random number between 1 and 19. But on refreshing the page in the browser, this number does not change. If I kill the server and re-initiate by running dev_appserver, I get a new random number. How do I get the random number to update on page refresh.

Code follows:

package testpage

import (
    "fmt"
    "net/http"
    "math/rand"
    "time"
    "strconv"
)

func init() {
    http.HandleFunc("/", handler)
}

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, varHtml)
}
func random(min, max int) int {
    rand.Seed(time.Now().Unix())
    return rand.Intn(max - min) + min
}

var myrand = strconv.Itoa(random(1, 19))
var varHtml = `

Random number is ` + myrand 

The varHtml is a package level variable and is calculated just once.

You should move it to the handler as:

func handler(w http.ResponseWriter, r *http.Request) {
    var varHtml = `Random number is ` + strconv.Itoa(random(1, 19))
    fmt.Fprint(w, varHtml)
}

Also there is no need to seed rand every time.

It's better to do it at package init():

func init() {
    rand.Seed(time.Now().Unix())
}

func random(min, max int) int {
    return rand.Intn(max - min) + min
}