add lib package and make task to build shared lib

Makefile

@@ -1,7 +1,16 @@
 .PHONY: test
 
+GOBIN=./build
+
 deps:
 	go get -t ./...
 
 test:
 	go test -v ./...
+
+keycard-lib: ##@cross-compile Build keycard-go as static library for current platform
+	mkdir -p $(GOBIN)/libkeycard
+	@echo "Building static library..."
+	go build -buildmode c-shared -o $(GOBIN)/libkeycard/libkeycard.so ./cmd/lib
+	@echo "Static library built:"
+	@ls -la $(GOBIN)/libkeycard/*

cmd/lib/main.go

@@ -0,0 +1,4 @@
+package main
+
+func main() {
+}