Deploying a Shiny app using a self-written package

I have a working shiny app which uses library(coral), where coral is a package I wrote myself, installed in the directory of the shiny app.

When I attempt to deploy my app onto shinyapps.io, I receive the following message:

Error: Unable to retrieve package records for the following packages:
- "coral"
Execution halted

From what I can gather online, the issue is probably that coral is not on CRAN, so shinyapps.io cannot get the records for that package from there.

Is that a correct description of the problem? And is there a simple solution?

Thanks in advance.