require("alias/file") works fine, but if you have an index file under the alias and reference only require("alias"), it doesn't work. Imports to the root of an alias never gets replaced.

From what I see, this project has been abandoned, if anyone goes through the same problem, you need to replace the line 105 in this file for:

if (modulePath.startsWith(prefix) || modulePath === prefix.replace(/\/$/, '')) {