Edit database urls in pgloader.ini then use run.sh, or use environment variables.
See here: https://pgloader.readthedocs.io/en/latest/command.html#templating-with-mustache
Read the comment at the start of the pgloader script file for an important note on how to fix json stuff before running pgloader.
As of September 2024 this works perfectly and has been used on a large production server. If it's become out of date since then, or you have any other support questions, feel free to contact me by opening an issue or on the SS14 discord @sgp10 (imcb).