API Gateway: Insert requestId into request body using mapping template

In AWS Api Gateway, I want to insert the generated requestId into the request body without having to manually type each entry in the original request body.

If this is the original request body:

{
  "name": "name",
  "age": "20",
  ...
}

Then I want to transform it into:

{
  "name": "name",
  "age": "20",
  ...,
  "requestId": $context.requsetId
}

I do realize that there is an option of inserting the id into the header, but I want to insert the requestId into the body instead. I also want to avoid typing each key-value in the original body because I want the requestId to be inserted regardless of the body structure.

You can use mapping templates to add the requestId to the request body.

I also want to avoid typing each key-value in the original body because I want the requestId to be inserted regardless of the body structure

You can use a template like this for that:

#set($inputRoot = $input.path('$'))
{
  #foreach($key in $inputRoot.keySet())
    "$key": "$inputRoot.get($key)"
    #if($foreach.hasNext),#end
  #end,
  "requestId":"$context.requestId"
}