Initial commit with Dockerfile and Go code

Dockerfile

@@ -0,0 +1,19 @@
+FROM golang:1.21-alpine AS builder
+
+WORKDIR /app
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY main.go ./
+RUN go build -o sshserver main.go
+
+FROM alpine:latest
+
+RUN apk add --no-cache ca-certificates
+
+COPY --from=builder /app/sshserver /usr/local/bin/sshserver
+
+EXPOSE 22
+
+CMD ["/usr/local/bin/sshserver"]