Support for Go 1.21

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# github.com/quic-go/quic-go/internal/qtls
../../../go/pkg/mod/github.com/quic-go/quic-go@v0.32.0/internal/qtls/go121.go:5:13: cannot use "The version of quic-go you're using can't be built on Go 1.21 yet. For more details, please see https://github.com/quic-go/quic-go/wiki/quic-go-and-Go-versions." (untyped string constant "The version of quic-go you're using can't be built on Go 1.21 yet. F...) as int value in variable declaration

Update quic-go to 0.37.4 .

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found the same problem