README: mysql.NullTime as an alternative to parseTime=true

[ymmt2005]

Description

parseTime=true cannot parse TIMESTAMP columns and has a subtle limitation.
mysql.NullTime is a great alternative to that option, so I think it is worth mentioning.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[shogo82148]

mysql.NullTime will be deprecated, so I recommend using sql.NullTime and the parseTime=true DSN option.

mysql/nulltime_go113.go

Lines 32 to 34 in e246959

	// Deprecated: NullTime doesn't honor the loc DSN parameter.
	// NullTime.Scan interprets a time as UTC, not the loc DSN parameter.
	// Use sql.NullTime instead.

parseTime=true cannot parse TIMESTAMP columns and has a subtle limitation.

Can you show me some examples about it ?
The driver can parse TIMESTAMP and it is tested.

mysql/driver_test.go

Lines 1551 to 1588 in 4d5208a

	func TestTimezoneConversion(t *testing.T) {
	zones := []string{"UTC", "US/Central", "US/Pacific", "Local"}
	// Regression test for timezone handling
	tzTest := func(dbt *DBTest) {
	// Create table
	dbt.mustExec("CREATE TABLE test (ts TIMESTAMP)")
	// Insert local time into database (should be converted)
	usCentral, _ := time.LoadLocation("US/Central")
	reftime := time.Date(2014, 05, 30, 18, 03, 17, 0, time.UTC).In(usCentral)
	dbt.mustExec("INSERT INTO test VALUE (?)", reftime)
	// Retrieve time from DB
	rows := dbt.mustQuery("SELECT ts FROM test")
	defer rows.Close()
	if !rows.Next() {
	dbt.Fatal("did not get any rows out")
	}
	var dbTime time.Time
	err := rows.Scan(&dbTime)
	if err != nil {
	dbt.Fatal("Err", err)
	}
	// Check that dates match
	if reftime.Unix() != dbTime.Unix() {
	dbt.Errorf("times do not match.\n")
	dbt.Errorf(" Now(%v)=%v\n", usCentral, reftime)
	dbt.Errorf(" Now(UTC)=%v\n", dbTime)
	}
	}
	for _, tz := range zones {
	runTests(t, dsn+"&parseTime=true&loc="+url.QueryEscape(tz), tzTest)
	}
	}

[ymmt2005]

@shogo82148
Thank you for letting me know.

I couldn't notice the deprecation because it is noted only for Go 1.13.
With Go 1.16 (and pkg.go.dev), NullTime doesn't show the deprecation notice.

Anyway, I'm closing this.

$ go version
go version go1.16.2 linux/amd64

$ go doc github.com/go-sql-driver/mysql.NullTime
package mysql // import "github.com/go-sql-driver/mysql"

type NullTime sql.NullTime
    NullTime represents a time.Time that may be NULL. NullTime implements the
    Scanner interface so it can be used as a scan destination:

        var nt NullTime
        err := db.QueryRow("SELECT time FROM foo WHERE id=?", id).Scan(&nt)
        ...
        if nt.Valid {
           // use nt.Time
        } else {
           // NULL value
        }

    This NullTime implementation is not driver-specific

func (nt *NullTime) Scan(value interface{}) (err error)
func (nt NullTime) Value() (driver.Value, error)