client io architecture

pkg/util/fs_unix.go

@@ -0,0 +1,15 @@
+//go:build unix || (js && wasm) || wasip1
+
+package util
+
+import "golang.org/x/sys/unix"
+
+// Writable reports whether path is Writable on Windows.
+//
+// Semantics:
+//   - for an existing regular file, it tries to open it for writing;
+//   - for an existing directory, it tries to create and remove a temp file inside it;
+//   - for other file types, it returns false with no error.
+func Writable(filepath string) (bool, error) {
+	return unix.Access(filepath, unix.W_OK) == nil, nil
+}