TSM: Rename while file is in Use in compact_test

[mvadu]

I am trying to implement mmap and tsm compatibility to Windows via PR #4981 to fix #4358.
But MustWriteTSM in compact_test.go is trying to rename a file which is in use (a possible file leak scenario, not supported by Windows) is preventing me from proceeding. Could somebody here help me to resolve the issue?

>go test -v ./tsdb/engine/tsm1 > %temp%\gotest.txt 2>&1

     --- FAIL: TestCompactor_Compact (0.00s)
 panic: create tsm file: rename C:\Users\Ady\AppData\Local\Temp\tsm1-test087429749\tsm1test014002000 C:\Users\Ady\AppData\Local\Temp\tsm1-test087429749\000000001-000000001.tsm: The process cannot access the file because it is being used by another process. [recovered]
    panic: create tsm file: rename C:\Users\Ady\AppData\Local\Temp\tsm1-test087429749\tsm1test014002000 C:\Users\Ady\AppData\Local\Temp\tsm1-test087429749\000000001-000000001.tsm: The process cannot access the file because it is being used by another process.

gotest.txt

The root cause is in below code compact_test.go:761 where file handle returned by MustTempFile is not closed before rename operation, which is failing in Windows. Simply closing that handle before rename fails the next write operation.

 func MustWriteTSM(dir string, gen int, values map[string][]tsm1.Value) string {
    f := MustTempFile(dir)
    newName := filepath.Join(filepath.Dir(f.Name()), tsmFileName(gen))
    if err := os.Rename(f.Name(), newName); err != nil {
        panic(fmt.Sprintf("create tsm file: %v", err))
    }