Cecylia reminded me that building the quic-go version is trickier because quic-go has an unstable API, and the version of quic-go currently being used in the Tor Browser build is API-incompatible with what you'll get if you just "go get" or "go build". The snowflake repo doesn't yet have a go.mod file to lock in specific versions.
So the build instructions are a little bit more involved: git clone https://git.torproject.org/pluggable-transports/snowflake.git cd snowflake git remote add dcf https://git.torproject.org/user/dcf/snowflake.git git fetch dcf git checkout 5eff0f3ba406eb7d8cd90711edab7de7d7bda4fa for d in broker proxy-go server; do (cd $d && go get); done (cd $GOPATH/src/github.com/lucas-clemente/quic-go && git checkout 907071221cf97f75398d9cf8b1174e94f56e8f96) (cd $GOPATH/src/github.com/marten-seemann/qtls && git checkout 65ca381cd298d7e0aef0de8ba523a870ec5a96fe) for d in broker proxy-go server; do (cd $d && go build); done
Alternatively, you can change IdleTimeout to MaxIdleTimeout in the quic.Config structures; I think that's the only API change.