Instantiate password map

auth.go

@@ -15,7 +15,7 @@ import (
 var (
 	passwordFile = flag.String("passwords", "/etc/nginx-authenticator/users.json", "JSON file with usernames/passwords")
 
-	passwords map[string]string
+	passwords = make(map[string]string)
 )
 
 func authenticate(username, password string) bool {