add github action, build script, docker ignore

Dockerfile

@@ -0,0 +1,12 @@
+FROM golang:1.23-bookworm AS builder
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+# Buildx automatically injects TARGETARCH, TARGETOS, and TARGETPLATFORM as build args into the Dockerfile
+ARG TARGETARCH
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=${TARGETARCH} go build -o go-weather .
+FROM gcr.io/distroless/static-debian12
+COPY --from=builder /app/go-weather /go-weather
+EXPOSE 8080
+ENTRYPOINT ["/go-weather"]