Hold on with upgrading to Go 1.14

[karalabe]

This is just a tracker issue to point people to if someone opens a PR to update to Go 1.14. Currently we're blocked by two issues:

• On some systems, building the docker images blows up: runtime: mlock of signal stack failed: 12 golang/go#37436, which lends to belief that not just Go, but anything built with it might blow up too. A lot of other projects are holding off from upgrading, so probably it's sane for us to do so too.
• The GC triggers were modified in Go 1.14, which means that the same GOGC configurations as we've had previously will consume more memory. runtime: high memory usage on Go 1.14 golang/go#37525 This might need some investigation, just chalking it up here as a potential OOM issue if we upgrade blindly.