added ability to specify port via env

main.go

@@ -4,10 +4,10 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"strconv"
 )
 
 const usage = "servetls <cert file> <key file>"
-const port = 8443
 
 func main() {
 	if len(os.Args) != 3 {
@@ -18,6 +18,15 @@ func main() {
 
 	http.HandleFunc("/", handler)
 
+	port := 8443
+	if os.Getenv("PORT") != "" {
+		p, err := strconv.Atoi(os.Getenv("PORT"))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "could not parse PORT variable: %s\n", os.Getenv("PORT"))
+			os.Exit(1)
+		}
+		port = p
+	}
 	addr := fmt.Sprintf(":%d", port)
 	fmt.Printf("serving on %s", addr)
 	err := http.ListenAndServeTLS(addr, cert, key, nil)