refactor: Decompose key checks

pkg/noop/flusher.go

@@ -0,0 +1,19 @@
+package noop
+
+import "io"
+
+type Flusher interface {
+	io.WriteCloser
+
+	Flush() error
+}
+
+type NoOpFlusher struct {
+	io.WriteCloser
+}
+
+func (NoOpFlusher) Flush() error { return nil }
+
+func AddFlush(w io.WriteCloser) NoOpFlusher {
+	return NoOpFlusher{w}
+}

pkg/noop/write.go

@@ -0,0 +1,13 @@
+package noop
+
+import "io"
+
+type NoOpCloser struct {
+	io.Writer
+}
+
+func (NoOpCloser) Close() error { return nil }
+
+func AddClose(w io.Writer) NoOpCloser {
+	return NoOpCloser{w}
+}