Replace megacheck with staticcheck tool megacheck tool is deprecated

.travis.yml

@@ -9,15 +9,14 @@ install:
   - go get github.com/stretchr/testify/assert
   - go get github.com/gordonklaus/ineffassign
   - go get github.com/fzipp/gocyclo
-  - go get honnef.co/go/tools/cmd/megacheck
+  - go get honnef.co/go/tools/cmd/staticcheck
 
 script:
   - test -z "$(gofmt -s -l . 2>&1 | grep -v vendor | tee /dev/stderr)"
   - go vet ./ ./conflate ./example
   - ineffassign ./ ./conflate ./example
   - gocyclo -over 15 ./*.go
-  - megacheck -simple.exit-non-zero=true -staticcheck.exit-non-zero=true -unused.exit-non-zero=true ./ ./conflate ./example
-  - megacheck -tests=false -simple.enabled=false -staticcheck.enabled=false -unused.exit-non-zero=true ./ ./conflate ./example
+  - staticcheck  --unused.whole-program -show-ignored -fail . ./conflate ./example/
   - go test -coverprofile .coverprofile
   - $GOPATH/bin/goveralls -v -coverprofile .coverprofile -service=travis-ci