runtime(gomod): add gomod filetype plugin

closes: #15060

Signed-off-by: yu-yk <yukkuen.yu@linktivity.co.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/MAINTAINERS b/.github/MAINTAINERS
index 5ebe93a..1957499 100644
--- a/.github/MAINTAINERS
+++ b/.github/MAINTAINERS
@@ -152,6 +152,7 @@
 runtime/ftplugin/graphql.vim	@ribru17
 runtime/ftplugin/gyp.vim		@ObserverOfTime
 runtime/ftplugin/go.vim			@dbarnett
+runtime/ftplugin/gomod.vim		@yu-yk
 runtime/ftplugin/gprof.vim		@dpelle
 runtime/ftplugin/haml.vim		@tpope
 runtime/ftplugin/hare.vim		@selenebun
diff --git a/runtime/ftplugin/gomod.vim b/runtime/ftplugin/gomod.vim
new file mode 100644
index 0000000..0d5d9ba
--- /dev/null
+++ b/runtime/ftplugin/gomod.vim
@@ -0,0 +1,14 @@
+" Vim filetype plugin file
+" Language:    go module file
+" Maintainer:  YU YUK KUEN <yukkuen.yu719@gmail.com>
+" Last Change: 2024-06-21
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setlocal formatoptions-=t formatoptions-=c
+setlocal commentstring=//\ %s
+
+let b:undo_ftplugin = 'setl fo< cms<'