add gruf worker pool

vendor/codeberg.org/gruf/go-runners/context.go

@@ -0,0 +1,36 @@
+package runners
+
+import (
+	"context"
+	"time"
+)
+
+// ContextWithCancel returns a new context.Context impl with cancel.
+func ContextWithCancel() (context.Context, context.CancelFunc) {
+	ctx := make(cancelctx)
+	return ctx, func() { close(ctx) }
+}
+
+// cancelctx is the simplest possible cancellable context.
+type cancelctx (chan struct{})
+
+func (cancelctx) Deadline() (time.Time, bool) {
+	return time.Time{}, false
+}
+
+func (ctx cancelctx) Done() <-chan struct{} {
+	return ctx
+}
+
+func (ctx cancelctx) Err() error {
+	select {
+	case <-ctx:
+		return context.Canceled
+	default:
+		return nil
+	}
+}
+
+func (cancelctx) Value(key interface{}) interface{} {
+	return nil
+}