add: cancel transfer

internal/transfer/reader.go

@@ -0,0 +1,21 @@
+package transfer
+
+import (
+	"context"
+	"io"
+)
+
+// ContextReader 带有 Context 的 Reader
+type ContextReader struct {
+	ctx context.Context
+	r   io.Reader
+}
+
+func (cr *ContextReader) Read(p []byte) (n int, err error) {
+	select {
+	case <-cr.ctx.Done():
+		return 0, cr.ctx.Err() // 返回 context.Canceled 错误
+	default:
+		return cr.r.Read(p)
+	}
+}