docker: build from go 1.12

[cameronattard]

Problem

httputil.ReverseProxy doesn't support WebSockets in go 1.11.

Solution

Build binaries using go 1.12.

Notes

I'm not sure if any additional changes are required to get WebSockets to work, but this is a start.

#103
https://go-review.googlesource.com/c/go/+/146437

[codecov]

Codecov Report

Merging #225 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #225   +/-   ##
=======================================
  Coverage   62.23%   62.23%           
=======================================
  Files          50       50           
  Lines        4067     4067           
=======================================
  Hits         2531     2531           
  Misses       1349     1349           
  Partials      187      187

[Jusshersmith]

Hey @cameronattard.

Thanks for sending this through! I’m working on validating this change now.

[Jusshersmith]

Thanks again for the contribution @cameronattard!

[cameronattard]

Thanks @Jusshersmith. Is there a revised ETA for the next release?

[Jusshersmith]

Hey @cameronattard - apologies for the delay of this release. We're aiming to release it any day now (by EOD tomorrow most likely), but I'll let you know if that changes.

Thanks for your patience!