.md content add in .toml

[kaushalmodi]

That needs to go in your layout file, not content file. The content files cannot contain bare Go templates (you can have them indirectly… by wrapping them up in shortcodes).

Related:

[SOLVED] Curly Brackets Not Rendering

You cannot do that. You can have only Shortcodes ({{< foo >}} or {{% bar %}}) in content files. The Go templating snippet you pasted would work only in layout files (files in layouts/ or themes/).