node: Basic graceful shutdown

lib/valctx/context.go

@@ -0,0 +1,28 @@
+package valctx
+
+import (
+	"context"
+	"time"
+)
+
+type Context struct {
+	Parent context.Context
+}
+
+func (c *Context) Deadline() (deadline time.Time, ok bool) {
+	return
+}
+
+func (c *Context) Done() <-chan struct{} {
+	return nil
+}
+
+func (c *Context) Err() error {
+	return nil
+}
+
+func (c *Context) Value(key interface{}) interface{} {
+	return c.Parent.Value(key)
+}
+
+var _ context.Context = &Context{}