feat: add post-response callbacks

internal/postresponse/callbacks.go

@@ -0,0 +1,53 @@
+package postresponse
+
+import (
+	"context"
+	"sync"
+)
+
+type callback func()
+
+type callbacksKey struct{}
+
+type callbacks struct {
+	mu   sync.Mutex
+	list []callback
+}
+
+func WithCallbacks(ctx context.Context) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	if _, ok := ctx.Value(callbacksKey{}).(*callbacks); ok {
+		return ctx
+	}
+	return context.WithValue(ctx, callbacksKey{}, &callbacks{})
+}
+
+func Register(ctx context.Context, cb func()) bool {
+	if cb == nil {
+		return false
+	}
+	cbs, ok := ctx.Value(callbacksKey{}).(*callbacks)
+	if !ok || cbs == nil {
+		return false
+	}
+	cbs.mu.Lock()
+	cbs.list = append(cbs.list, cb)
+	cbs.mu.Unlock()
+	return true
+}
+
+func Run(ctx context.Context) {
+	cbs, ok := ctx.Value(callbacksKey{}).(*callbacks)
+	if !ok || cbs == nil {
+		return
+	}
+	cbs.mu.Lock()
+	list := append([]callback(nil), cbs.list...)
+	cbs.list = nil
+	cbs.mu.Unlock()
+	for _, cb := range list {
+		cb()
+	}
+}