Fix panic in filecache

[ghost]

Hi!

We've got panic happened while liniting our repository with golangci-lint. The reason is concurrent writes in filecache map. I tried to fix it via using sync.Map instead of map, so there must be no concurrent [read/]writes. Also there might be possible race in linecache because there is no any mutex either.

Panic

if [ "Darwin" = "Darwin" ]; then export PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig/; else export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig/; fi && \
	golangci-lint run -c golangci_extended.yml -v  ./src/mail/...
level=info msg="[config_reader] Used config file golangci_extended.yml"
level=info msg="[lintersdb] Active 29 linters: [bodyclose deadcode depguard dupl errcheck goconst gocritic gocyclo gofmt goimports golint gosec gosimple govet ineffassign interfacer lll misspell nakedret prealloc scopelint staticcheck structcheck stylecheck typecheck unconvert unparam unused varcheck]"
level=info msg="[lintersdb] Optimized sublinters [staticcheck gosimple unused stylecheck] into metalinter megacheck"
level=info msg="[loader] Go packages loading at mode load types and syntax took 19.223275966s"
level=info msg="[loader] SSA repr building timing: packages building 266.546786ms, total 6.847481739s"
src/mail/api/clickerproxy/vid.go:59:42: bodyclose: response body must be closed (bodyclose)
	resp, err := requests.BaseOnce().Request(ctx, req, requests.Params{
	                                        ^
fatal error: concurrent map writes

goroutine 10801 [running]:
runtime.throw(0x1a8048f, 0x15)
	/usr/local/go/src/runtime/panic.go:617 +0x72 fp=0xc0020916a0 sp=0xc002091670 pc=0x102e862
runtime.mapassign_faststr(0x18efd40, 0xc000468420, 0xc000517560, 0x51, 0x1742)
	/usr/local/go/src/runtime/map_faststr.go:211 +0x42a fp=0xc002091708 sp=0xc0020916a0 pc=0x1014e5a
github.com/golangci/golangci-lint/pkg/fsutils.(*FileCache).GetFileBytes(0xc00046e0c8, 0xc000517560, 0x51, 0xc166d77500, 0x991, 0xc034f46c80, 0x0, 0x8)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/fsutils/filecache.go:33 +0x10b fp=0xc002091798 sp=0xc002091708 pc=0x140ce4b
github.com/golangci/golangci-lint/pkg/golinters.Misspell.runOnFile(0xc000517560, 0x51, 0xc002091b18, 0xc1644e5f00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/golinters/misspell.go:68 +0x61 fp=0xc0020919f8 sp=0xc002091798 pc=0x17e3311
github.com/golangci/golangci-lint/pkg/golinters.Misspell.Run(0x1bde7c0, 0xc000032f60, 0xc1644e5f00, 0xc03caf4860, 0x1, 0x1, 0x1bacdd4, 0xc000054990)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/golinters/misspell.go:56 +0x1cc fp=0xc002091b58 sp=0xc0020919f8 pc=0x17e2b7c
github.com/golangci/golangci-lint/pkg/golinters.(*Misspell).Run(0x24136c8, 0x1bde7c0, 0xc000032f60, 0xc1644e5f00, 0xc120e73e90, 0x203048, 0x10228d5, 0x0, 0x1870ebcb)
	<autogenerated>:1 +0x58 fp=0xc002091ba8 sp=0xc002091b58 pc=0x17ea758
github.com/golangci/golangci-lint/pkg/lint.(*Runner).runLinterSafe(0xc002091ee0, 0x1bde7c0, 0xc000032f60, 0xc03cb06000, 0xc0003d1d00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:112 +0x16a fp=0xc002091ca8 sp=0xc002091ba8 pc=0x180bc4a
github.com/golangci/golangci-lint/pkg/lint.Runner.runWorker.func1()
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:146 +0x64 fp=0xc002091d18 sp=0xc002091ca8 pc=0x180d924
github.com/golangci/golangci-lint/pkg/timeutils.(*Stopwatch).TrackStage(0xc03bea4280, 0x1a129c6, 0x8, 0xc002091e40)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/timeutils/stopwatch.go:75 +0x50 fp=0xc002091d78 sp=0xc002091d18 pc=0x1806d40
github.com/golangci/golangci-lint/pkg/lint.Runner.runWorker(0xc03c910000, 0x11, 0x11, 0x1be8880, 0xc03ca64c90, 0x1bde7c0, 0xc000032f60, 0xc03cb06000, 0xc03caeea80, 0xc03caeec00, ...)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:145 +0x23b fp=0xc002091ee0 sp=0xc002091d78 pc=0x180c00b
github.com/golangci/golangci-lint/pkg/lint.(*Runner).runWorkers.func1(0xc02c718490, 0xc03ca30270, 0x1bde7c0, 0xc000032f60, 0xc03cb06000, 0xc03caeea80, 0xc03caeec00, 0xc03bb96480, 0x8, 0x8, ...)
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:200 +0x163 fp=0xc002091f88 sp=0xc002091ee0 pc=0x180db53
runtime.goexit()
	/usr/local/go/src/runtime/asm_amd64.s:1337 +0x1 fp=0xc002091f90 sp=0xc002091f88 pc=0x105d091
created by github.com/golangci/golangci-lint/pkg/lint.(*Runner).runWorkers
	/Users/ndr/go/src/gitlab.corp.mail.ru/e-mail-ru/mailapi/vendor/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:197 +0x1ab

Full output of this run is here

https://gist.github.com/be-b10g/6be369a6ff3a237496c6fca004487566

[CLAassistant]

All committers have signed the CLA.

[jirfag]

thank you very much for the fix!

[jirfag]

Also, I will try to enable tests with -race for master branch builds (too slow for regular branch builds)