Change effective on 13 April 2016
Heroku has added support for Go v1.6.1 and v1.5.4.
These are now the default version of Go when
go1.5 is specified in an application’s
Godeps/Godeps.json file (for godep),
$GOVERSION (for GB) environment variable, or
vendor/vendor.json file (for govendor) and will be used on next push.
These versions of Go address security issues that are unlikely to affect most Heroku users of Go, but we encourage all users to re-deploy their application(s) to take advantage of these updates.
For more information, see our Dev Center article on Heroku Go Support.