client.go
func OptImportThreadCount(count int) ImportOption {
	return func(options *ImportOptions) error {
		options.threadCount = count
		return nil
	}
}
func OptImportThreadCount(count int) ImportOption {
	return func(options *ImportOptions) error {
		options.threadCount = count
		return nil
	}
}
// OptImportThreadCount is the number of goroutines allocated for import.