Switch to fmt.Sprintf for appending a newline in CommandRun for consistency

internal/batch/command.go

@@ -1,6 +1,7 @@
 package batch
 
 import (
+	"fmt"
 	"strings"
 
 	"git.kor-elf.net/kor-elf-shield/go-nftables-client/contract"
@@ -18,6 +19,6 @@ func NewCommand(file *pkg.File) contract.CommandRun {
 }
 
 func (c *commandRun) Run(args ...string) error {
-	_, err := c.file.Write([]byte(strings.Join(args, " ")))
+	_, err := c.file.Write([]byte(fmt.Sprintf("%s\n", strings.Join(args, " "))))
 	return err
 }