db.sql

CREATE TABLE data (id serial primary key, name text, data jsonb);
INSERT INTO data (name, data) VALUES ('testing', '{"foo": 1, "bar": 2}');
INSERT INTO data (name, data) DEFAULT VALUES;

out.txt

ants@ants-ThinkPad:~/tmp/test-conn$ go run test.go 
Output json for testing(1): {"Id":1,"Name":"testing","Data":{"bar":2,"foo":1}}
Unmarshaled to Id=1 Name=testing Data={"bar":2,"foo":1}
Output json for <null>(2): {"Id":2,"Name":null,"Data":null}
Unmarshaled to Id=2 Name=<null> Data=<<<NULL>>>

test.go

package main

import (
	"context"
	"fmt"
	"database/sql"
	_ "github.com/lib/pq"
	"encoding/json"
)

type MyData struct {
	Id int
	Name *string
	Data *json.RawMessage
}

func coalesce(input *string, default_value string) string {
	if input == nil {
		return default_value
	}
	return *input
}

func main() {
	// In main part of the application
	db, err := sql.Open("postgres", "dbname=postgres host=localhost sslmode=disable user=postgres")
	defer db.Close()
	checkErr(err)

	// In single request
	tx, err := db.BeginTx(context.Background(), &sql.TxOptions{sql.LevelRepeatableRead, false})
	checkErr(err)
	rows, err := tx.Query("SELECT id, name, data FROM data") // Run query in that transaction
	checkErr(err)

	for rows.Next() {
		var obj MyData
		checkErr(rows.Scan(&obj.Id, &obj.Name, &obj.Data))
		jsonOut, err := json.Marshal(obj)
		checkErr(err)

		fmt.Printf("Output json for %v(%v): %v\n", coalesce(obj.Name, "<null>"), obj.Id, string(jsonOut))

		var obj2 MyData
		checkErr(json.Unmarshal(jsonOut, &obj2))

		var data string
		if obj2.Data != nil {
			data = string(*obj2.Data)
		} else {
			data = "<<<NULL>>>"
		}
		fmt.Printf("Unmarshaled to Id=%v Name=%v Data=%s\n", obj2.Id, coalesce(obj2.Name, "<null>"), data)
	}
	// doStuffWith(rows)
	rows.Close()

	checkErr(tx.Commit())

}

func checkErr(err error) {
	if err != nil {
		panic(err)
	}
}