Invalid json unmarshal for pgtype.Timestamp

[s-montigny-desautels]

Describe the bug
pgtype.Timestamp use time.RFC3338Nano which expects timezone information. However, postgres don't return timezone information from a timestamp without time zone. As such:

select to_json(now()::timestamp without time zone) ;
           to_json            
------------------------------
 "2024-09-23T16:14:51.152496"

To Reproduce
Steps to reproduce the behavior:

package main

import (
	"context"
	"log"
	"os"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgtype"
)

func main() {
	conn, err := pgx.Connect(context.Background(), os.Getenv("DATABASE_URL"))
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close(context.Background())

	row := conn.QueryRow(context.Background(), "select to_json(now()::timestamp)")
	var strTime string
	if err := row.Scan(&strTime); err != nil {
		panic(err)
	}

	var t pgtype.Timestamp
	if err := json.Unmarshal([]byte(strTime), &t); err != nil {
		panic(err) <-- panic here
	}
}

Expected behavior
pgtype.Timestamp parse the format of the timestamp returned by postgres

Actual behavior
pgtype.Timestamp expect timezone information from the string, but timestamp don't have timezone information.

panic: parsing time "2024-09-23T16:07:53.607446" as "2006-01-02T15:04:05.999999999Z07:00": cannot parse "" as "Z07:00"

Version

• Go: go version go1.23.1 linux/amd64
• PostgreSQL: PostgreSQL 16.3 on x86_64-pc-linux-gnu, compiled by Debian clang version 12.0.1, 64-bit
• pgx: 5.7.1