[pkg-go] golang-github-rsc-letsencrypt is marked for autoremoval from testing

[Debian testing autoremoval watch]

golang-github-rsc-letsencrypt 0.0~git20160929.0.76104d2-3 is marked for autoremoval from testing on 2018-01-09

It (build-)depends on packages with these RC bugs:
882554: golang-google-grpc: golang-google-grpc FTBFS: stringer: checking package: code_string.go:5:8: could not import fmt (can't find import: )