Syncthing broken by go-1.15 + quic

Great!

I’ve just tried building the 1.9.0-rc.3 tag and got the same error:

panic: qtls.ConnectionState doesn't match

goroutine 1 [running]:
github.com/marten-seemann/qtls-go1-15.init.0()
        github.com/marten-seemann/qtls-go1-15@v0.1.0/unsafe.go:11 +0x245

That’s using go1.15beta1. I’m a little behind, but should have worked, right?