technoweenie/go-contentaddressable — pull request #2 by technoweenie (2014-10-30 22:26:19+00:00)
Title: don't try to close the temp file twice, otherwise Close() returns an error

```
--- FAIL: TestFile (0.00 seconds)
file_test.go:171: /Users/rick/p/go-contentaddressable/file_test.go:37
Expected:
Actual: invalid argument
```

The invalid argument came from trying to close the `w.tempFile` twice. This sets it to nil so an extra `w.Close()` doesn't return an error.