fix: update autotls example. (#965)

README.md

@@ -910,7 +910,7 @@ func main() {
 		Cache:      autocert.DirCache("/var/www/.cache"),
 	}
 
-	log.Fatal(autotls.RunWithManager(r, m))
+	log.Fatal(autotls.RunWithManager(r, &m))
 }
 ```
 

examples/auto-tls/example2.go

@@ -22,5 +22,5 @@ func main() {
 		Cache:      autocert.DirCache("/var/www/.cache"),
 	}
 
-	log.Fatal(autotls.RunWithManager(r, m))
+	log.Fatal(autotls.RunWithManager(r, &m))
 }