travis workaround go1.14 issue

workaround for golang/go#35589

Author: Jan Unterbrink

.travis.yml

@@ -30,6 +30,7 @@ jobs:
       before_script:
         - curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | BINARY=golangci-lint sh -s -- -d -b $(go env GOPATH)/bin v1.23.7
         - export GO111MODULE=on
+        - export GOFLAGS=-mod=mod
         - sudo apt-get install jq -y
       script:
         - make verify