diff --git a/Plugging-in-Plugins-Yourself.md b/Plugging-in-Plugins-Yourself.md
index d20d456..5aaf470 100644
--- a/Plugging-in-Plugins-Yourself.md
+++ b/Plugging-in-Plugins-Yourself.md
@@ -20,5 +20,5 @@ func main() {
 	caddymain.Run()
 }
 ```
-5. Make your little main function a Go module: `go mod init mycaddy` (the name doesn't really matter).
+5. Make your little main function a Go module: `go mod init mycaddy` (the name doesn't really matter, but the filename should end in `.go`).
 6. Then `go install` will then create your binary at `$GOPATH/bin`, or `go build` will put it in the current directory.