add warning using http2 example (gin-gonic#1009)

Author: thinkerou

examples/http2/main.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"html/template"
+	"log"
+	"os"
 
 	"github.com/gin-gonic/gin"
 )
@@ -18,6 +20,9 @@ var html = template.Must(template.New("https").Parse(`
 `))
 
 func main() {
+	logger := log.New(os.Stderr, "", 0)
+	logger.Println("[WARNING] DON'T USE THE EMBED CERTS FROM THIS EXAMPLE IN PRODUCTION ENVIRONMENT, GENERATE YOUR OWN!")
+
 	r := gin.Default()
 	r.SetHTMLTemplate(html)