chore: initialize go module and cmd skeleton

cmd/supervisor/main.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	fmt.Fprintln(os.Stderr, "supervisor: not yet implemented")
+	os.Exit(1)
+}

cmd/supervisor/main_test.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"os/exec"
+	"testing"
+)
+
+func TestBinaryCompiles(t *testing.T) {
+	cmd := exec.Command("go", "build", "./...")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("build failed: %s\n%s", err, out)
+	}
+}

go.mod

@@ -0,0 +1,3 @@
+module github.com/mathiasbq/supervisor
+
+go 1.26.1