golf and also securing

cmd/createkeyfile/main.go

@@ -53,22 +53,13 @@ func main() {
 		quit(err.Error())
 	}
 
-	_, err = os.Open(keyfilePath)
-	if err == nil {
-		quit(fmt.Sprintf("%s already exists", keyfilePath))
-	}
-
-	f, err := os.Create(keyfilePath)
+	f, err := os.OpenFile(keyfilePath, os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
 	if err != nil {
-		quit(err.Error())
+		quit(fmt.Sprintf("failed to open %s: %s", keyfilePath, err.Error()))
 	}
 
 	defer f.Close()
 
-	if err = os.Chmod(keyfilePath, os.FileMode(0600)); err != nil {
-		quit(err.Error())
-	}
-
 	stdin := make([]byte, 90000) // arbitrary limit
 
 	n, err := os.Stdin.Read(stdin)