I use an add-on called Codeblocks. It lets you select a block of text and will format it as monospace w/ syntax highlighting in various themes. Not quite as go

I use an add-on called Codeblocks. It lets you select a block of text and will format it as monospace w/ syntax highlighting in various themes. Not quite as good as native support (e.g. doesn't update dynamically), but otherwise it's pretty solid.