My reproduction program for https://github.com/golang/go/issues/10886

db-failure.go

package main

import (
	"database/sql"
	"fmt"
	_ "github.com/VividCortex/mysql"
	"net/http"
	_ "net/http/pprof"
	"time"
)

const numConnToOpen = 5

func main() {
	startTime := time.Now()
	defer func() {
		fmt.Printf("Exiting after %vs\n", time.Now().Sub(startTime).Seconds())
	}()

	go func() {
		fmt.Println(http.ListenAndServe(":6060", nil))
	}()

	db, err := sql.Open("mysql", "root:password@tcp(1.2.3.4:3306)/mysql?timeout=2s")
	if err != nil {
		fmt.Println(err)
	}

	db.SetMaxOpenConns(2)
	db.SetMaxIdleConns(0)
	done := make(chan bool, numConnToOpen)
	for i := 0; i < numConnToOpen; i++ {
		go func() {
			err := db.Ping()
			if err != nil {
				fmt.Println(err)
			}
			fmt.Printf("Done in %vs\n", time.Now().Sub(startTime).Seconds())
			done <- true
		}()
	}

	for i := 0; i < numConnToOpen; i++ {
		<-done
	}
}