Update golang

Changes:

- https://github.com/docker-library/golang/commit/151ac2e: Merge pull request https://github.com/docker-library/golang/pull/300 from infosiftr/1.13-stretch
- https://github.com/docker-library/golang/commit/e7c5f60: Add stretch variant for 1.13
- https://github.com/docker-library/golang/commit/1e0c17d: Update generated README

library/golang

@@ -11,6 +11,11 @@ Architectures: amd64, arm32v7, arm64v8, i386, ppc64le, s390x
 GitCommit: 2909cfd3ecb769671eb8222eaf9a782a6aed024d
 Directory: 1.13/buster
 
+Tags: 1.13.0-stretch, 1.13-stretch, 1-stretch, stretch
+Architectures: amd64, arm32v7, arm64v8, i386, ppc64le, s390x
+GitCommit: e7c5f6049153f4f754eff210413b1d7ea882ad72
+Directory: 1.13/stretch
+
 Tags: 1.13.0-alpine3.10, 1.13-alpine3.10, 1-alpine3.10, alpine3.10, 1.13.0-alpine, 1.13-alpine, 1-alpine, alpine
 Architectures: amd64, arm32v6, arm32v7, arm64v8, i386, ppc64le, s390x
 GitCommit: 2909cfd3ecb769671eb8222eaf9a782a6aed024d