set TRAVIS_BUILD_NUMBER

Author: Igor Olshevsky

.travis.yml

@@ -8,7 +8,7 @@ install:
 - go test -i ./...
 - go get -u github.com/mitchellh/gox
 - mkdir release
-- cd release && gox -arch 'amd64' -os 'linux windows darwin' -ldflags "-X main.version=$TRAVIS_TAG" ../src/...
+- cd release && gox -arch 'amd64' -os 'linux windows darwin' -ldflags "-X main.version=$TRAVIS_BUILD_NUMBER" ../src/...
 script:
 - cd $TRAVIS_BUILD_DIR
 - go test -race -v ./...