You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: dblock_test.go
    path of file: ./repos/arvados/lib/controller/dblock
    
    the code of the file until where you have to start completion: // Copyright (C) The Arvados Authors. All rights reserved.
//
// SPDX-License-Identifier: AGPL-3.0

package dblock

import (
	"bytes"
	"context"
	"sync"
	"testing"
	"time"

	"git.arvados.org/arvados.git/lib/config"
	"git.arvados.org/arvados.git/sdk/go/arvados"
	"git.arvados.org/arvados.git/sdk/go/arvadostest"
	"git.arvados.org/arvados.git/sdk/go/ctxlog"
	"github.com/jmoiron/sqlx"
	"github.com/sirupsen/logrus"
	check "gopkg.in/check.v1"
)

func Test(t *testing.T) {
	check.TestingT(t)
}

var _ = check.Suite(&suite{})

type suite struct {
	cluster *arvados.Cluster
	db      *sqlx.DB
	getdb   func(context.Context) (*sqlx.DB, error)
}

var test
    
func (s *suite) TestLock(c *check.C) {
	retryDelay = 10 * time.Millisecond

	var logbuf bytes.Buffer
	logger := ctxlog.New(&logbuf, "text", "debug")
	logger.Level = logrus.DebugLevel
	ctx := ctxlog.Context(context.Background(), logger)
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()
	testLocker.Lock(ctx, s.getdb)
	testLocker.Check()

	lock2 := make(chan bool)
	var wg sync.WaitGroup
	defer wg.Wait()
	wg.Add(1)
	go func() {
		defer wg.Done()
		testLocker2 := &DBLocker{key: 999}
		testLocker2.Lock(ctx, s.getdb)
		close(lock2)
		testLocker2.Check()
		testLocker2.Unlock()
	}()

	// Second lock should wait for first to Unlock
	select {
	case <-time.After(time.Second / 10):
		c.Check(logbuf.String(), check.Matches, `(?ms).*level=info.*DBClient="[^"]+:\d+".*ID=999.*`)
	case <-lock2:
		c.Log("double-lock")
		c.Fail()
	}

	testLocker.Check()
	testLocker.Unlock()

	// Now the second lock should succeed within retryDelay
	select {
	case <-time.After(retryDelay * 2):
		c.Log("timed out")
		c.Fail()
	case <-lock2:
	}
	c.Logf("%s", logbuf.String())
}