How can we check that a string considered to be a MySQL TIMESTAMP is actually valid? The format used is:

YYYY-MM-DD HH:MM:SS[.fraction] where "fraction" has 3 digits.

For example 2016-03-28 12:17:30.022 should be valid. Preferably I would like to avoid regex and use time.Parse() but any other suggestion is welcome.

Call time.Parse with a layout string such as "2006-01-02 15:04:05.999" on your time string. If that results in a valid time.Time value and no error then your string should work in the db.

timeStamp, err := time.Parse("2006-01-02 15:04:05.999", yourTimeString)
    if err != nil {
        // do something with err...
    }
// do something with timeStamp...

I don't use MySQL but between PostgreSQL and Go you can pass around timestamps and time.Time values without converting to strings... so maybe that simplifies your problem. Covert the string in Go using time.Parse and then write the time.Time value to the db.

You can use TIMESTAMP() to convert the string to timestamp. If it can be converted to a valid timestamp, it is valid. If converted to NULL, then it is not a void timestamp string.

Use:

TIMESTAMP('2016-03-28 12:17:30.022') IS NOT NULL

Demo

mysql> select TIMESTAMP('2016-03-28 12:17:30.022'), TIMESTAMP('2016-03-28 12:17:300.022');
+--------------------------------------+---------------------------------------+
| TIMESTAMP('2016-03-28 12:17:30.022') | TIMESTAMP('2016-03-28 12:17:300.022') |
+--------------------------------------+---------------------------------------+
| 2016-03-28 12:17:30.022              | NULL                                  |
+--------------------------------------+---------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> select TIMESTAMP('2016-03-28 12:17:30.022') IS NOT NULL, TIMESTAMP('2016-03-28 12:17:300.022') IS NOT NULL;
+--------------------------------------------------+---------------------------------------------------+
| TIMESTAMP('2016-03-28 12:17:30.022') IS NOT NULL | TIMESTAMP('2016-03-28 12:17:300.022') IS NOT NULL |
+--------------------------------------------------+---------------------------------------------------+
|                                                1 |                                                 0 |
+--------------------------------------------------+---------------------------------------------------+
1 row in set, 1 warning (0.00 sec)

As @Snowman pointed out in his comment, one solution is by using a layout string and time.Parse()

package main

import (
  "fmt"
  "time"
)

func main() {

  timestamp    := "2016-03-28 11:50:50.476"
  const layout  = "2006-01-02 03:04:05.999"

  _, error := time.Parse(layout, timestamp)

  if error != nil {
    fmt.Println(error)
  } else {
    fmt.Println("valid!")
  }
}

Demo: https://play.golang.org/p/6bcciN_OAb
Also check: Date parsing in Go