deploy to heroku with docker and github action

Dockerfile

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+FROM golang:1.13 AS builder
+
+WORKDIR /src
+COPY . /src
+
+RUN CGO_ENABLED=0 GOOS=linux go build -o npqueue .
+
+# ---
+
+FROM heroku/heroku:18
+
+WORKDIR /app
+COPY --from=builder /src /app
+
+ENV GIN_MODE=release
+
+CMD ["./npqueue"]