The gallows is an old image of public judgement. In dreams it is read symbolically, as fear of being condemned or of a harsh verdict on something you did, not as a forecast of anything.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.