Update to golang 1.11.3 (elastic#9560)

* Update to golang 1.11.3

cmd/go: remote command execution during "go get -u"
The issue is CVE-2018-16873 and Go issue golang.org/issue/29230. See the Go issue for details.
Thanks to Etienne Stalmans from the Heroku platform security team for discovering and reporting this issue.

cmd/go: directory traversal in "go get" via curly braces in import paths
The issue is CVE-2018-16874 and Go issue golang.org/issue/29231. See the Go issue for details.
Thanks to ztz of Tencent Security Platform for discovering and reporting this issue.

crypto/x509: CPU denial of service in chain validation
The issue is CVE-2018-16875 and Go issue golang.org/issue/29233. See the Go issue for details.
Thanks to Netflix for discovering and reporting this issue.

https://golang.org/doc/devel/release.html#go1.11.minor

* Changelog

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.11.2
+FROM golang:1.11.3
 MAINTAINER Noémi Ványi <noemi.vanyi@elastic.co>
 
 RUN set -x && \