Copying files to a created container

Docker Engine General
1

I am trying to copy files to a created container (not running), using the docker go SDK

snippet:

func (c *DkClient) CopyToContainer(containerID string, tarPath string) error {
    log.Debug().Msgf("Copying files to container %s", containerDirectory)

    tarStream, err := os.Open(tarPath)
    if err != nil {
       return err
    }

    c.client.Cop

    err = c.client.CopyToContainer(
       context.Background(),
       containerID,
       containerDirectory,
       tarStream,
       container.CopyToContainerOptions{AllowOverwriteDirWithFile: true},
    )
    if err != nil {
       log.Error().Err(err).Msgf("failed to copy to Docker container")
       return fmt.Errorf("failed to copy submission to container")
    }

    return nil
}

But I get the following error

Error response from daemon: Could not find the file /home/test/test.tar.gz in container ....

If I use docker cp it works

docker cp .\test.tar.gz <contId>:/home/test/test.tar.gz

Successfully copied 8.19kB to :/home/test/test.tar.gz

Anyone know why this is happening thanks !!