What am I doing wrong in this frame

[fils]

Given the code

package main

import (
	"encoding/json"
	"fmt"
	"log"

	"github.com/piprate/json-gold/ld"
)

func main() {
	fmt.Println("Frame testing")

	data := mockDataEvent()

	x := simpleFrame(data)
	log.Println(x)
}

// simpleFrame is a simple testing frame
func simpleFrame(jsonld string) string {
	proc := ld.NewJsonLdProcessor()
	options := ld.NewJsonLdOptions("")

	frame := map[string]interface{}{
		"@context":   map[string]interface{}{"@vocab": "https://schema.org/"},
		"@explicit":  true,
		"@type":      "Dataset",
		"identifier": "",
		"license":    "",
		"version":    "",
	}

	var myInterface interface{}
	err := json.Unmarshal([]byte(jsonld), &myInterface)
	if err != nil {
		log.Println("Error when transforming JSON-LD document to interface:", err)
	}

	framedDoc, err := proc.Frame(myInterface, frame, options) // do I need the options set in order to avoid the large context that seems to be generated?
	if err != nil {
		log.Println("Error when trying to frame document", err)
	}

	graph := framedDoc["@graph"]
	// ld.PrintDocument("JSON-LD graph section", graph) // debug print....

	jsonm, err := json.MarshalIndent(graph, "", " ")
	if err != nil {
		log.Println("Error trying to marshal data", err)
	}

	return string(jsonm)
}

// mockDataEvent  returns example JSONLD for local testing if needed
func mockDataEvent() string {

	data := ` {
"@context": {"@vocab":  "https://schema.org/"},
"@type": "Dataset",
"@id": "https://example.org/datasets/1234567890",
"identifier": "doi:10.1234/1234567890",
"name": "Removal of organic carbon by natural bacterioplankton communities as a function of pCO2 from laboratory experiments between 2012 and 2016",
"description": "A description between 50 and 5000 characters.",
"url": "https://example.org/datasets/1234567890",
"version": "2013-11-21",
"keywords": ["ocean acidification", "OA", "oceans"],
"license": "CC-BY-4.0",
"sameAs": "https://doi.org/10.1234/1234567890"
}`

	return data

}

When I run this I get

❯ go run frameTest2.go
Frame testing
2023/04/28 20:24:01 [
 {
  "@id": "https://example.org/datasets/1234567890",
  "@type": "Dataset",
  "identifier": null,
  "license": null,
  "version": null
 }
]
❯ 

Putting that frame and JSON-LD into https://json-ld.org/playground/
returns

{
  "@context": {
    "@vocab": "https://schema.org/"
  },
  "@id": "https://example.org/datasets/1234567890",
  "@type": "Dataset",
  "identifier": "doi:10.1234/1234567890",
  "license": "CC-BY-4.0",
  "version": "2013-11-21"
}

which is what I expected. Am I encoding the frame wrong in my code?

[fils]

OK.. so

	frame := map[string]interface{}{
		"@context":   map[string]interface{}{"@vocab": "https://schema.org/"},
		"@type":      "Dataset",
		"@explicit":  true,
		"identifier": map[string]interface{}{"@default": "default value"},
		"license":    map[string]interface{}{"@default": "default value"},
		"version":    map[string]interface{}{"@default": "default value"},
	}

but still curious why the "" approach doesn't work?