GoSublime was just updated so first make sure you have the latest (restart Sublime Text or find "Package Control: Upgrade Package" from the Goto -> Goto Anything menu.
Now you can use the "Goto Anything" menu again and narrow down the options by typing "GoSublime", or use GS's own "Goto Anything" style menu (cmd-., cmd. on Mac, maybe ctrl-. ctrl. on PC?)
In there you find Show Errors (cmd-., cmd-e). Also you can place your cursor on the line with an error (marked by dot in gutter) and look at the status bar - it shows the error.
Show documentation hint (cmd-., cmd-h) is supposed give the godoc in a panel below the editor but doesn't seem to work reliably for me (it has in the past). Also there is Goto Definition (cmd., cmd-g) which opens the file and jumps to the definition of the item under cursor.
Show Call tip (cmd-., cmd-space) shows the function-under-cursor's parameters in a panel below the editor. You can dismiss these panels with ESC.
Personally I also use Add/Remove package (cmd-., cmd-p) all the time.