added closer package

closer/closer.go

@@ -0,0 +1,37 @@
+package closer
+
+import (
+	"context"
+)
+
+type Closer interface {
+	Close(ctx context.Context) error
+}
+
+type CloserFunc func(ctx context.Context) error
+
+func (cf CloserFunc) Close(ctx context.Context) error {
+	return cf(ctx)
+}
+
+type CloserGroup struct {
+	closers []Closer
+}
+
+func NewCloserGroup() *CloserGroup {
+	return &CloserGroup{}
+}
+
+func (cg *CloserGroup) Add(c Closer) {
+	cg.closers = append(cg.closers, c)
+}
+
+func (cg *CloserGroup) Call(ctx context.Context) error {
+	var closeErr error
+	for i := len(cg.closers) - 1; i >= 0; i-- {
+		if err := cg.closers[i].Close(ctx); err != nil && closeErr == nil {
+			closeErr = err
+		}
+	}
+	return closeErr
+}