Data race on _escFile.name#65

I hit this data race in my CI: ``` ================== WARNING: DATA RACE Read at 0x00c0000d2a68 by goroutine 7: github.com/hortbot/hortbot/internal/db/migrations/esc.(*_escFile).Name() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/esc/esc.go:130 +0x3e github.com/golang-migrate/migrate/v4/source/httpfs.(*PartialDriver).Init() /home/travis/gopath/pkg/mod/github.com/golang-migrate/migrate/[email protected]/source/httpfs/partial_driver.go:48 +0x34c github.com/golang-migrate/migrate/v4/source/httpfs.New() /home/travis/gopath/pkg/mod/github.com/golang-migrate/migrate/[email protected]/source/httpfs/driver.go:21 +0xaf github.com/hortbot/hortbot/internal/db/migrations.newMigrate() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/migrations.go:51 +0x77 github.com/hortbot/hortbot/internal/db/migrations.Up() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/migrations.go:15 +0x8d github.com/hortbot/hortbot/internal/db/migrations_test.withDatabase() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/migrations_test.go:67 +0x11e github.com/hortbot/hortbot/internal/db/migrations_test.TestUp() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/migrations_test.go:33 +0x52 testing.tRunner() /home/travis/.gimme/versions/go/src/testing/testing.go:993 +0x1eb Previous write at 0x00c0000d2a68 by goroutine 77: github.com/hortbot/hortbot/internal/db/migrations/esc._escStaticFS.prepare.func1() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/esc/esc.go:59 +0xad sync.(*Once).doSlow() /home/travis/.gimme/versions/go/src/sync/once.go:66 +0x103 sync.(*Once).Do() /home/travis/.gimme/versions/go/src/sync/once.go:57 +0x68 github.com/hortbot/hortbot/internal/db/migrations/esc._escStaticFS.prepare() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/esc/esc.go:58 +0x160 github.com/hortbot/hortbot/internal/db/migrations/esc._escStaticFS.Open() /home/travis/gopath/src/github.com/hortbot/hortbot/internal/db/migrations/esc/esc.go:78 +0x46 github.com/hortbot/hortbot/internal/db/migrations/esc.(*_escStaticFS).Open() <autogenerated>:1 +0x5f github.com/golang-migrate/migrate/v4/source/httpfs.(*PartialDriver).ReadUp() /home/travis/gopath/pkg/mod/github.com/golang-migrate/migrate/[email protected]/source/httpfs/partial_driver.go:111 +0x1b9 github.com/golang-migrate/migrate/v4/source/httpfs.(*driver).ReadUp() <autogenerated>:1 +0x5b github.com/golang-migrate/migrate/v4.(*Migrate).newMigration() /home/travis/gopath/pkg/mod/github.com/golang-migrate/migrate/[email protected]/migrate.go:837 +0x96 github.com/golang-migrate/migrate/v4.(*Migrate).readUp() /home/travis/gopath/pkg/mod/github.com/golang-migrate/migrate/[email protected]/migrate.go:612 +0x22b ``` It appears as though there's a path where the static file is being returned before it has been prepared, but I can't see how at first glance.