Have service listen and server over TLS

Pass in command line arguments to the path of the certificate and key
files.

what-is-my-ip.go

@@ -14,7 +14,7 @@ import (
 func main() {
 	app := cli.NewApp()
 	app.Name = "what-is-my-ip"
-	app.Version = "0.1.0"
+	app.Version = "0.2.0"
 	app.Usage = "Webapp that gives the IP address for incoming requests"
 	app.Action = action
 
@@ -25,6 +25,20 @@ func main() {
 			EnvVar: "WHAT_IS_MY_IP_ADDRESS",
 			Usage:  "Address and port to bind to",
 		},
+
+		cli.StringFlag{
+			Name:   "certificate, c",
+			Value:  "cert.pem",
+			EnvVar: "WHAT_IS_MY_IP_CERTIFICATE",
+			Usage:  "path to certificate file for https server",
+		},
+
+		cli.StringFlag{
+			Name:   "key, k",
+			Value:  "key.pem",
+			EnvVar: "WHAT_IS_MY_IP_KEY",
+			Usage:  "path to key file for https server",
+		},
 	}
 
 	app.Run(os.Args)
@@ -33,8 +47,10 @@ func main() {
 func action(c *cli.Context) error {
 	http.HandleFunc("/", getIP)
 	address := c.String("address")
+	certificate := c.String("certificate")
+	key := c.String("key")
 	fmt.Printf("listening on %s\n", address)
-	return http.ListenAndServe(address, nil)
+	return http.ListenAndServeTLS(address, certificate, key, nil)
 }
 
 func getIP(w http.ResponseWriter, req *http.Request) {