Revert "use Go 1.14's embedded interfaces, update CIs"

[Stebalien]

This reverts commit c88a690.

Unfortunately, go 1.14's new scheduler and timer changes have a few bugs that need to be ironed out before it's ready for production use.

See:

• Sudden stall at 100% CPU libp2p/go-libp2p#858
• runtime: starvation with frequent timer resets golang/go#38119

[Stebalien]

Looks like we'll also need to downgrade qtls.

[marten-seemann]

@Stebalien Looking at the discussion in golang/go#38119, is my understanding correct that we don't need to do this downgrade as long as we compile everything with Go 1.14.2?

[Stebalien]

I'd still like to downgrade. Unfortunately, it's unclear when 1.14.2 will be released (and the go-ipfs release is already late). Furthermore, I expect these won't be the last bugs in 1.14.2 as it has quite a few changes to critical parts of the go scheduler.

[marten-seemann]

This is a situation that Go Modules seems not well equipped to handle.

The issue here is that in Go 1.14, crypto/tls made some significant changes regarding the certificate selection, e.g. by adding additional fields and functions to the tls.ClientHelloInfo (which I then transferred over to qtls). If we want to downgrade to Go 1.13, we also have to downgrade qtls to an earlier version. Which means that users of quic-go who use Go 1.14 will find those new features broken / not implemented.

As far as I can see, there's no way of telling Go to use version x of a dependency when built with Go 1.13 and version y if built with Go 1.14. Or am I missing something?

[Stebalien]

You'd either have to release a qtls version with go 1.13 support using build flags, or downgrade. We can also do this in a set of separate branches.

[lucas-clemente]

Can you just downgrade quic-go to the previous version in libp2p?

[marten-seemann]

Not really. We need the qlogs to evaluate and debug transfers, and that only added in the last few weeks.