change golang version

build/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.8.1
+FROM golang:1.8.7-stretch
 
 # Support Raspberry Pi 2 and newer
 ENV GOARM 7

vagrant-common.rb

@@ -16,7 +16,7 @@ def ansibleize(h)
 end
 
 def get_go_version_from_build_dockerfile()
-  go_regexp = /FROM golang:(\S*).*?/
+  go_regexp = /FROM golang:([\d\.]*).*?/
   dockerfile_path = File.expand_path(File.join(File.dirname(__FILE__), 'build', 'Dockerfile'))
   go_version = File.readlines(dockerfile_path).select { |line| line.match(go_regexp) }.first.match(go_regexp).captures.first
   if go_version.nil?