JSON load failed with lib/pq

json_pq_error.go

package main

import (
	"database/sql"
	"encoding/json"
	"fmt"

	_ "github.com/lib/pq"
)

type Article struct {
	Id  int
	Doc *json.RawMessage
}

func main() {
	db, err := sql.Open("postgres", "postgres://localhost/json_test?sslmode=disable")
	if err != nil {
		panic(err)
	}

	_, err = db.Query(`create table if not exists articles (id serial primary key, doc json)`)
	if err != nil {
		panic(err)
	}
	_, err = db.Query(`truncate articles`)
	if err != nil {
		panic(err)
	}
	docs := []string{
		`{"type":"event1"}`,
		`{"type":"event2"}`,
	}
	for _, doc := range docs {
		_, err = db.Query(`insert into articles ("doc") values ($1)`, doc)
		if err != nil {
			panic(err)
		}
	}

	rows, err := db.Query(`select id, doc from articles`)
	if err != nil {
		panic(err)
	}

	articles := make([]Article, 0)

	for rows.Next() {
		var a Article
		err := rows.Scan(
			&a.Id,
			&a.Doc,
		)
		if err != nil {
			panic(err)
		}
		articles = append(articles, a)
        fmt.Println("scan", string(*a.Doc), len(*a.Doc))
	}

    fmt.Println()

    for _, a := range articles {
        fmt.Println("loop", string(*a.Doc), len(*a.Doc))
    }
}

result

Expected:
scan {"type":"event1"} 17
scan {"type":"event2"} 17

loop {"type":"event1"} 17
loop {"type":"event2"} 17

But I got:
scan {"type":"event1"} 17
scan {"type":"event2"} 17

loop {"type":"event2"} 17
loop {"type":"event2"} 17

After the appends, the docs are all the same