ci: Update golangci-lint

See golangci/golangci-lint#658.

Author: foxcpp

.travis.yml

@@ -10,7 +10,7 @@ env:
 - GO111MODULE=on
 
 install:
-- curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $GOPATH/bin v1.16.0
+- curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $GOPATH/bin v1.18.0
 
 script:
 - go test ./... -race -coverprofile=coverage.txt -covermode=atomic