Segmentation fault during high load

[tobbe76]

During high load bazel-remote sometimes(every second day) crash, i believe this due to #771. Buffer is returned to early in some cases.
If "recvResult" returns error then we may exit before the go func() handling s.cache.Put.

We switched back to use #770 instead of #771 and has been running for over 2weeks now without any crashes.

Log:
2024/10/07 09:15:59 Failed to mark /data/cas.v2/29/295c2c111a05828bce5f4a7844986e2b02f4977125f8a861f22f5607b6d9e5f8-1795516-119705455 as complete: chmod /data/cas.v2/29/295c2c111a05828bce5f4a7844986e2b02f4977125f8a861f22f5607b6d9e5f8-1795516-119705455: no such file or directory
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xec pc=0x795c0a]

goroutine 773401358 [running]:
github.com/klauspost/compress/zstd.(*blockDec).decodeBuf(0x0, 0xc5e507f020)
external/com_github_klauspost_compress/zstd/blockdec.go:232 +0x2a
github.com/klauspost/compress/zstd.(*Decoder).nextBlockSync(0xc4288d6300)
external/com_github_klauspost_compress/zstd/decoder.go:508 +0x4f5
github.com/klauspost/compress/zstd.(*Decoder).nextBlock(0xc4288d6300, 0x0?)
external/com_github_klauspost_compress/zstd/decoder.go:420 +0x49
github.com/klauspost/compress/zstd.(*Decoder).Read(0xc4288d6300, {0xcfc80d2000?, 0xc7d3315000?, 0x0?})
external/com_github_klauspost_compress/zstd/decoder.go:145 +0x13c
github.com/klauspost/compress/zstd.closeWrapper.Read({0xc5a18db7e8?}, {0xcfc80d2000?, 0x4f9051?, 0xc7b8ab9b00?})
external/com_github_klauspost_compress/zstd/decoder.go:616 +0x18
io.ReadAtLeast({0x7f77761b2e88, 0xc7b8aed170}, {0xcfc80d2000, 0x100000, 0x100000}, 0x100000)
GOROOT/src/io/io.go:335 +0x90
io.ReadFull(...)
GOROOT/src/io/io.go:354
github.com/buchgr/bazel-remote/v2/cache/disk/casblob.WriteAndClose({0x12a8a58, 0x19fae40}, {0x7f77761b2e88, 0xc7b8aed170}, 0xc7a9a74ab0, 0x1, {0xc78519f873, 0x40}, 0x21976)
cache/disk/casblob/casblob.go:628 +0x7a7
github.com/buchgr/bazel-remote/v2/cache/disk.(*diskCache).writeAndCloseFile(0xc7b9054660?, {0x12a8358, 0xc8bc114210}, {0x7f77761b2e88?, 0xc7b8aed170?}, 0xc8bc115770?, {0xc78519f873?, 0x33?}, 0x21976, 0xc7a9a74ab0)
cache/disk/disk.go:365 +0x114
github.com/buchgr/bazel-remote/v2/cache/disk.(*diskCache).Put(0xc00033e400, {0x12a8358, 0xc8bc114210}, 0x1, {0xc78519f873, 0x40}, 0x21976, {0x7f77761b2e88, 0xc7b8aed170})
cache/disk/disk.go:328 +0x6e7
github.com/buchgr/bazel-remote/v2/server.(*grpcServer).Write.func2.1()
server/grpc_bytestream.go:456 +0xc9
created by github.com/buchgr/bazel-remote/v2/server.(*grpcServer).Write.func2 in goroutine 773389695
server/grpc_bytestream.go:455 +0x13f8