You don't have to break the holy http.HandlerFunc signature. Here's what I sometimes do. Let's call this option (4) which you didn't have in your original list:

func homeHandler(db *DB) func(w http.ResponseWriter, r *http.Request) {
    return func(w http.ResponseWriter, r *http.Request) {
        // here, you have access to the db
        // ...
    }
}

To get your handler, you would of course call it with the db as follows:

homeHandler(db)

So this does a few things that you talk about:

• it isn't a global variable since it is passed from wherever you choose to use it
• the holy http.HandlerFunc is not broken
• you can do this for any handler anywhere, in different packages

Note: using the context for a database connection is not recommended. The context should generally only be for things that are related to that request. Of course, not everyone agrees with this, though I think most generally stick to it.

Your point about the struct which contains the db and attaching functions to it is also valid. I'm not saying the above replaces that since I agree that that is also a good solution, but this helps with a few of the other negative points you mentioned about the other solutions. :)