Missing shared library libpq.so.5

[dchenk]

When I build my app on the debian:buster-slim Docker image and run it I get an error while loading shared libraries: libpq.so.5: cannot open shared object file: No such file or directory.

What is my image missing, or is it possible to build the app with this library linked statically?

[weiznich]

This error message indicates quite clearly that you miss a package that provides libpq. Please search the debian package repository how the package is called there.
The Readme of pq-sys provides a few more details about different link options.