如何在2秒内让golang mysql驱动程序ping超时？

I am having some trouble figuring out how to make a database connection-attempt timeout properly in Go. I am using some of the examples at this excellent resource as a base. I believe I am setting up everything correctly, but my pings just refuse to time out after 2 seconds. I've extracted the code in question into a sample program as follows. Note that there is no database running at 172.1.2.3.

package main

import (
    "context"
    "database/sql"
    _ "github.com/go-sql-driver/mysql" //MySQL driver
    "log"
    "time"
)

func main() {
    log.Print("Trying to ping database!")

    //Prepare a "context" to execute queries in, this will allow us to use timeouts
    var bgCtx = context.Background()
    var ctx2SecondTimeout, cancelFunc2SecondTimeout = context.WithTimeout(bgCtx, time.Second*2)
    defer cancelFunc2SecondTimeout()

    //Open  database connection
    db, err := sql.Open("mysql", "root:@tcp(172.1.2.3)/testdb?parseTime=true")
    if err != nil {
        log.Printf("Unable to open db, %s", err.Error())
        return
    }
    log.Print("Successfully called open()")

    //Ping database connection with 2 second timeout
    err = db.PingContext(ctx2SecondTimeout)
    if err != nil {
        log.Printf("Can't ping database server in order to use storage, %s", err.Error())
        return
    }
    log.Print("Successfully pinged database!")
}

Running the program should take up to about 2 seconds, but instead it takes 2+ minutes:

$ go run lambdatry.go
2018/09/03 16:33:33 Trying to ping database!
2018/09/03 16:33:33 Successfully called open()
2018/09/03 16:35:43 Can't ping database server in order to use storage, dial tcp 172.1.2.3:3306: connect: connection timed out

If I change the IP of the "database" (I just picked a random IP so there's no database at this address) the database sometimes times out immediately and sometimes takes a really long time to timeout.

I am running go 1.10.1 on ubuntu 18.04.

Could it be this issue: https://github.com/golang/go/issues/27476 ?

My issue is slightly different, it times out one 1s but not 2s or 3s! https://media.dev.unee-t.com/2018-09-05/pingcontext.mp4

My source is here: https://media.dev.unee-t.com/2018-09-05/main.go