Loki zstd compression - memory leak due to increasing go-routines

[bharath-sadhu]

Hi Team,

zstd compression in loki is causing memory leaks

goroutine profile: total 7031
2211 @ 0x47526e 0x40a05c 0x409c32 0xc0fe7b 0x47dac1
#	0xc0fe7a	github.com/klauspost/compress/zstd.(*Decoder).startStreamDecoder.func2+0x9a	/src/loki/vendor/github.com/klauspost/compress/zstd/decoder.go:714

2211 @ 0x47526e 0x40a05c 0x409c32 0xc105b9 0x47dac1
#	0xc105b8	github.com/klauspost/compress/zstd.(*Decoder).startStreamDecoder.func1+0x78	/src/loki/vendor/github.com/klauspost/compress/zstd/decoder.go:658

2193 @ 0x47526e 0x450d25 0xc0f88e 0x47dac1
#	0xc0f88d	github.com/klauspost/compress/zstd.(*Decoder).startStreamDecoder+0x7ad	/src/loki/vendor/github.com/klauspost/compress/zstd/decoder.go:872

Above is the go-routine profile for one of the querier running in k8s with 44 GB memory utilisation with out any queries running now, and in that querier out of total 7031 goroutines running 95% are from zstd and they are not getting closed properly causing memory to increase in queriers