Golang MySQL connection with multiple IPs and connection timeouts

gistfile1.go

package main

import (
	"database/sql"
	"fmt"
	"github.com/go-sql-driver/mysql"
	"log"
	"net/http"
	"strings"
	"time"
	"net"
	"math/rand"
)

const (
	pxc_hosts   string = `pxc.service.consul:3306`
	user               = `test`
	pass               = `test`
	schema             = `sakila`
	options            = `timeout=500ms`
	max_idle    int    = 0 // Can't keep idle conns open b/c of: https://github.com/go-sql-driver/mysql/issues/257
	concurrency        = 10 // Keep this script from blasting the database
	retry_delay        = 500 * time.Millisecond
	lag = 50 * time.Millisecond
)

// Our global writer DB handle
var writer *sql.DB
var hits int

func main() {	
	var err error
	// Setup our SQL pool
	writer, err = sql.Open(`mysql`,
		fmt.Sprintf("%s:%s@tcp(%s)/%s?%s", user, pass, pxc_hosts,
			schema, options))
	if err != nil {
		log.Fatal("Got ", err, "trying to connect to writer")
	}
	writer.SetMaxIdleConns(max_idle)
	writer.SetMaxOpenConns(concurrency)
	mysql.RegisterDial( `tcp`, func( addr string ) (net.Conn, error) {	
		host, port, err := net.SplitHostPort( addr )  // MUST have the port component
		if err != nil {
			return nil, &net.OpError{Op: "dial", Net:`tcp`, Addr: nil, Err: err}
		}
	
		addrs, err := net.LookupHost( host )
		if err != nil {
			return nil, &net.OpError{Op: "dial", Net:`tcp`, Addr: nil, Err: err}
		}

		selected := addrs[rand.Intn(len(addrs))]
		fmt.Println( "Selected: ", selected )
	
		timeout, _ := time.ParseDuration(`500ms`)
		nd := net.Dialer{Timeout: timeout }
		
		conn, err := nd.Dial(`tcp`, net.JoinHostPort( selected, port ))
		if err != nil {
			return nil, &net.OpError{Op: "dial", Net:`tcp`, Addr: nil, Err: err}
		}
		// Close the connection after 10 seconds to force the pool to reconnect
		// this isn't necessarily graceful, but it seems mostly ok.  
		go func() {
			time.Sleep( 10 * time.Second )
			conn.Close()
		}()
		
		return conn, nil
	})
	defer writer.Close()

Do you need a goroutine to expire connections?

golang/go#9851

Went a little fast there, woops. The above issue mentions SetConnMaxLifetime

Does this caches connections from different databases?