Bug: race condition in tests

[roseduan]

reproduce the problem:

go test -race -test.run TestDB_Merge_6_Appending  -v ./

then an error occurred:

WARNING: DATA RACE
Read at 0x00c001146be8 by goroutine 6:
  github.com/rosedblabs/go-immutable-radix/v2.(*Node[...]).getEdge()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/go-immutable-radix/v2@v2.0.1-0.20230614125820-f2a7bc058c90/node.go:72 +0x4a
  github.com/rosedblabs/go-immutable-radix/v2.(*Node[...]).GetWatch()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/go-immutable-radix/v2@v2.0.1-0.20230614125820-f2a7bc058c90/node.go:119 +0x124
  github.com/rosedblabs/go-immutable-radix/v2.(*Node[...]).Get()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/go-immutable-radix/v2@v2.0.1-0.20230614125820-f2a7bc058c90/node.go:139 +0xa6
  github.com/rosedblabs/go-immutable-radix/v2.(*Tree[...]).Get()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/go-immutable-radix/v2@v2.0.1-0.20230614125820-f2a7bc058c90/iradix.go:654 +0x3b
  github.com/rosedblabs/rosedb/v2/index.(*IRadixTree).Get()
      /Users/roseduan/GoProjects/rosedb/index/iradix.go:32 +0x64
  github.com/rosedblabs/rosedb/v2.(*DB).Merge()
      /Users/roseduan/GoProjects/rosedb/merge.go:84 +0x4a1
  fmt.Sscanf()
      /usr/local/go/src/fmt/scan.go:114 +0x595
  github.com/rosedblabs/wal.Open()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/wal@v1.2.1-0.20230720135650-d5d56517e0a3/wal.go:98 +0x48d
  github.com/rosedblabs/rosedb/v2.(*DB).openMergeDB()
      /Users/roseduan/GoProjects/rosedb/merge.go:143 +0x254
  github.com/rosedblabs/rosedb/v2.(*DB).loadIndexFromHintFile()
      /Users/roseduan/GoProjects/rosedb/merge.go:316 +0x165
  github.com/rosedblabs/rosedb/v2.Open()
      /Users/roseduan/GoProjects/rosedb/db.go:115 +0x7bb
  fmt.Fscanf()
      /usr/local/go/src/fmt/scan.go:143 +0xe9
  fmt.Sscanf()
      /usr/local/go/src/fmt/scan.go:114 +0x595
  github.com/rosedblabs/wal.Open()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/wal@v1.2.1-0.20230720135650-d5d56517e0a3/wal.go:98 +0x48d
  github.com/rosedblabs/rosedb/v2.Open()
      /Users/roseduan/GoProjects/rosedb/db.go:94 +0x416
  github.com/rosedblabs/rosedb/v2.(*DB).openMergeDB()
      /Users/roseduan/GoProjects/rosedb/merge.go:137 +0x164
  github.com/rosedblabs/rosedb/v2.(*DB).Merge()
      /Users/roseduan/GoProjects/rosedb/merge.go:62 +0x197
  github.com/rosedblabs/rosedb/v2.TestDB_Merge_6_Appending()
      /Users/roseduan/GoProjects/rosedb/merge_test.go:183 +0x92b
  github.com/rosedblabs/rosedb/v2.(*DB).loadIndexFromHintFile()
      /Users/roseduan/GoProjects/rosedb/merge.go:316 +0x165
  github.com/rosedblabs/rosedb/v2.Open()
      /Users/roseduan/GoProjects/rosedb/db.go:115 +0x7bb
  fmt.Fscanf()
      /usr/local/go/src/fmt/scan.go:143 +0xe9
  fmt.Sscanf()
      /usr/local/go/src/fmt/scan.go:114 +0x595
  github.com/rosedblabs/wal.Open()
      /Users/roseduan/go/pkg/mod/github.com/rosedblabs/wal@v1.2.1-0.20230720135650-d5d56517e0a3/wal.go:98 +0x48d
  github.com/rosedblabs/rosedb/v2.Open()
      /Users/roseduan/GoProjects/rosedb/db.go:94 +0x416
  github.com/rosedblabs/rosedb/v2.TestDB_Merge_6_Appending()
      /Users/roseduan/GoProjects/rosedb/merge_test.go:147 +0xf9
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:1576 +0x216
  testing.(*T).Run.func1()
      /usr/local/go/src/testing/testing.go:1629 +0x47

[roseduan]

Fixed in #234 by @Jeremy-Run
Thanks.