I had the same problem, so I wrote my own function for it.
```
function! OpenURL()
    " store url in register a:
    norm 0"ayiW
    let url = @a

    " then open url in firefox:
    call feedkeys(':!bash firefox ' . url . ' &' . "\<CR>\<ESC>" )
endfunction

nnoremap gx :call OpenURL()<CR>
```