ci: Update golangci-lint

See golangci/golangci-lint#658.

Author: foxcpp

.travis.yml

@@ -13,7 +13,7 @@ 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:
 - golangci-lint run -E megacheck,deadcode,typecheck,govet,misspell,prealloc,gofmt,gocyclo,goconst,dupl,unconvert,interfacer,unparam