role postgres does not exist - attempting to connect to psql inside Express app - node.js

Question

There are similar questions with the one I have, but I'm still having trouble figuring out this issue.
I've added psql bin path to my bash_profile (on Mac) and I can run psql by:
psql -U postgres
The problem I have is that I can't run it inside my Express app. following the instructions on Express documentations, I have the following code:
const dotenv = require('dotenv').config();
var pgp = require('pg-promise')();
var db = pgp(
`postgres://
${process.env.DB_USER}:${process.env.DB_PASSWORD}
#
${process.env.DB_HOST}:5432/${process.env.DB_DATABASE}`
);
module.exports = db;
Then I try to make the db connection in app.js by
var db = require('./models/dbConnection/postgres')
db.one('SELECT $1 AS value', 123)
.then(function (data) {
console.log('DATA:', data.value)
})
.catch(function (error) {
console.log('ERROR:', error)
})
I have defined my environment variables in my .env file as follows:
DB_CONLIMIT=50
DB_HOST=127.0.0.1
DB_USER=postgres
DB_PASSWORD=
DB_DATABASE=mydatabase
when I run the app, I get:
[nodemon] starting node ./bin/www local-library:server Listening
on port 3000 +0ms ERROR: error: role "
postgres" does not exist
at Parser.parseErrorMessage
looking at my user table in psql when I run it via terminal:
postgres=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
postgres | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
What am I missing?