Merge pull request #3428 from hashicorp/go-1.9

Upgrades Go version to 1.9.

README.md

@@ -42,7 +42,7 @@ https://www.consul.io/docs
 ## Developing Consul
 
 If you wish to work on Consul itself, you'll first need [Go](https://golang.org)
-installed (version 1.8+ is _required_). Make sure you have Go properly installed,
+installed (version 1.9+ is _required_). Make sure you have Go properly installed,
 including setting up your [GOPATH](https://golang.org/doc/code.html#GOPATH).
 
 Next, clone this repository into `$GOPATH/src/github.com/hashicorp/consul` and

scripts/consul-builder/Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu:trusty
 
-ENV GOVERSION 1.8.3
+ENV GOVERSION 1.9
 
 RUN apt-get update -y && \
     apt-get install --no-install-recommends -y -q \