Hello all,
The feature being requested in this issue is syntax highlighting for html template code in Go files. Language features for such code like code completion and navigation is being discussed in #228
I do see the merits of this feature, although I am afraid I don't believe this extension is the right place for it anymore.
As VS Code and this extension has gained popularity, we have seen a gradual scope creep over the past two years. Being a sole maintainer of this project, it is getting a little hard to support all incoming requests and maintaining the ever growing set of features.
Moreover, this extension does not own or maintain the grammar that powers the syntax highlighting on Go files which comes out of the box from VS Code. This was previously based on https://github.com/atom/language-go and now moving towards https://github.com/jeff-hykin/better-go-syntax/ as being discussed in microsoft/vscode#82549
Therefore, it makes sense to have the grammar to support html template come from the same source or at the very least a separate extension.
Another alternative would be to make this feature request in the upstream VS Code repo. It might be labelled as extension-candidate meaning that this feature is better implemented as a separate extension in which case one can ask for pointers on how to go about doing that, perhaps based on the jsx support in VS Code.
My apologies and thanks for your patience.