Accessing data and global variables

[alic2o]

I wonder if some one can help me. Being new at using slate, I followed documentation as per instructions by setting a global variable in config.rb as follow

# Global Variables
set :document_root, 'docs'
config[:document_root]

I then tried to access it as <%= config[:document_root] %> in layout.erb. However, it throws error

NameError at /
undefined local variable or method `document_root' for #<#<Class:0x000055556c4fb430>:0x000055556dda9568>

I also tried to use local data files in project as per Middleman instructions. But that doesnt work either. Any help would be appreciated

By the way i am using slate in docker environment