Minimum Test Case

main.go

package main

import (
	"encoding/json"
	"log"
)

const j = `{
	"expectation": "Verbalizes understanding",
	"description": "Home Medication Administration Plan",
	"duration": null,
	"duration_unit": null,
	"offset_qty": "0.0",
	"offset_unit": null,
	"concept_cki": null
}`

type outcome struct {
	Duration     int
	DurationUnit string `json:"duration_unit"`
	Description  string `json:"description"`
	Expectation  string
	OffsetQty    string `json:"offset_qty"`
	OffsetUnit   string `json:"offset_unit"`
}

func main() {
	var o outcome
	json.Unmarshal([]byte(j), &o)
	log.Print(o)
}