It looks like the error message is correct: what you've posted here is not a valid JSON. Are you using an export mapping for your JSON or just building up the string manually?
This would be a valid JSON with the info you just posted here:
{
"name":"ABC",
"number":123
}
Edit: you edited your post after I posted this answer so it's no longer valid. The original post was missing quotes in the JSON message.
I read that you used an export mapping, and it worked.
The template would have worked too, if you would have removed the last }
So the correct template would have been
{{
"name": "Josesph",
"q": "12345"
}
Because it’s a template, you need to escape { with {{. You don’t need to escape }.