You have not given us enough information to be able to give any sensible answers. What actually is the task you want to do?
Go is just a programming language and HDMI is just a means of getting graphics, video, etc displayed.
I don't know of any graphics libraries written in Go. But if you want to create a GUI application with dialog boxes, buttons, sliders, etc there are things like this Go binding for the Qt GUI library.
If you want to play video using an external program as suggested above is probably the way to go.