Is there an option to change the base path for source mapping ?

I have posted this question to gopherjs group:

https://groups.google.com/forum/#!topic/gopherjs/OUwaLUH1jiU

My gopherjs-based application is built with: gopherjs install negentropia\negoc

It runs from: http://localhost:8080/ne/

Source mapping points to absolute base path: /negentropia/negoc
Like this: http://localhost:8080/negentropia/negoc/main.go

How can I point the source mapping base path elsewhere?
I want to add the /ne prefix like this:
http://localhost:8080/ne/negentropia/negoc/main.go

1. Is there an option to make the base path relative?
   I mean, how to remove the leading "/" from the source mapping path?

2. Otherwise, is there a way to prepend the /ne prefix to the absolute path?
   For example, how to change it to /ne/negentropia/negoc ?