max@morpheus:~/crystal/taxgod$ crystal run src/taxgod.cr
Unhandled exception: Duplicate trail found ‚vat-correction‘ (Radix::Tree::DuplicateError)
from lib/radix/src/radix/tree.cr:0:11 in ‚add‘
from lib/radix/src/radix/tree.cr:149:11 in ‚add‘
from lib/radix/src/radix/tree.cr:149:11 in ‚add‘
from lib/radix/src/radix/tree.cr:108:9 in ‚add‘
from lib/kemal/src/kemal/route_handler.cr:49:7 in ‚add_to_radix_tree‘
from lib/kemal/src/kemal/route_handler.cr:21:7 in ‚add_route‘
from lib/kemal/src/kemal/dsl.cr:12:1 in ‚post‘
from src/vatcorrection.cr:26:2 in ‚__crystal_main‘
from /usr/share/crystal/src/crystal/main.cr:97:5 in ‚main_user_code‘
from /usr/share/crystal/src/crystal/main.cr:86:7 in ‚main‘
from /usr/share/crystal/src/crystal/main.cr:106:3 in ‚main‘
from __libc_start_main
from _start
from ???

This Crystal error means that you have a function which is defined twice. For instance there’s a collision between functions in two modules which you included in the namespace.