This is an alternative emacs plugin, uses company-mode:
	http://nschum.de/src/emacs/company-mode

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

(require 'company)                                   ; load company mode
(require 'company-go)                                ; load company mode go backend and hook it up
(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 'company-backends'. By default company mode loads
every backend it has and it takes a huge amount of time to do so. I don't like
when my emacs takes more than 1 second to load, therefore I use a local variable
in company-go.el which contains only one backend (that is company-go
backend). Therefore if you want to use more company mode backends together with
company-go backend, you'll have to change that in company-go.el.

In other words, company-go.el does this:

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

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.