Here’s how I solved this.
When you run gigalixir pg it gives you the “url” field. Simply type pg_dump in terminal and paste the URL, then --file=file_name_you_want
pg_dump postgresql://username:password@host/database --file=my_dump.sql
Once it downloads simply run
psql -d myapp_dev -f my_dump.sql
myapp_dev being the name of your db in the dev.exs file.
Not sure if it matters, but before I did this I ran mix ecto.drop and mix ecto.create to start with a fresh db.
