Vercel will generate a set of PostgreSQL environment variables - the one we’re after here is POSTGRES_PASSWORD. Find its value, copy it, then put the password into psql.
This is the error I get when using the POSTGRES_PASSWORD: pg_dump: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: FATAL: password authentication failed for user "anthony"
And this is the command I am running: pg_dump db.sql | psql "postgres://default:<secret>@ep-green-hat-a41ooa8g.us-east-1.aws.neon.tech:5432/verceldb"