This is an alternative emacs plugin, uses company-mode:
	http://company-mode.github.io

Here's how I use it in my .emacs:

(require 'company)                                   ; load company mode
(require 'company-go)                                ; load company mode go backend
(setq company-tooltip-limit 20)                      ; bigger popup window
(setq company-minimum-prefix-length 0)               ; autocomplete right after '.'
(setq company-idle-delay .3)                         ; shorter delay before autocompletion popup
(setq company-echo-delay 0)                          ; removes annoying blinking
(setq company-begin-commands '(self-insert-command)) ; start autocompletion only after typing

One thing to note here is the 'company-backends' list. By default company mode
loads every backend it has. And while I could simply add company-go backend to
that list using a hook, I'm leaving it to the end user. Perhaps it would be
preferrable for you to use multiple backends at the same time, or maybe you
just want the company-go backend only in the go-mode. I prefer to use the
company-go backend only and having company-mode enabled only for go-mode.
That's the way you can do it:

(add-hook 'go-mode-hook (lambda ()
                          (set (make-local-variable 'company-backends) '(company-go))
                          (company-mode)))

I hope you get the idea.

P.S. Also, default company mode colors are kind of ugly, I took these from
auto-complete-mode defaults:

(custom-set-faces
 '(company-preview
   ((t (:foreground "darkgray" :underline t))))
 '(company-preview-common
   ((t (:inherit company-preview))))
 '(company-tooltip
   ((t (:background "lightgray" :foreground "black"))))
 '(company-tooltip-selection
   ((t (:background "steelblue" :foreground "white"))))
 '(company-tooltip-common
   ((((type x)) (:inherit company-tooltip :weight bold))
    (t (:inherit company-tooltip))))
 '(company-tooltip-common-selection
   ((((type x)) (:inherit company-tooltip-selection :weight bold))
    (t (:inherit company-tooltip-selection)))))

Of course you can change them the way you prefer, use customize-mode or do it manually.