How do I connect to a GCP PostgreSQL 11 DB in Project A from a go1.12 Flex Instance in Project B using gorm - postgresql

Question

Some preface:
I do not have access to the project that hosts the postgres DB.
The person who has access to the project and who set up the DB is unable to work with me directly on this. I have been told that they've followed the GCP documentation and that things are set up correctly on their end.
I am able to connect from my local deploy of the app because the person who set up the DB instance allowed my IP address; this doesn't work for an app engine flex deploy.
Problem:
I have an app engine flex instance built on golang 1.12. It connects to a postgreSQL 11 DB Cloud SQL instance in another project using github.com/jinzhu/gorm with the following code:
dbUri := fmt.Sprintf("host=%s user=%s dbname=%s password=%s", dbHost, dbUsername, dbName, dbPassword)
conn, err := gorm.Open("postgres", dbUri)
if err != nil {
log.Printf("Database error: %+v\n", err)
}
The dbhost is currently in the format of the DB's ip address.
I have tried /cloudsql/project:region:instance
I have tried /cloudsql/project:region:instance/.s.pgsql.5432
The relevant settings from the app.yaml I'm using:
beta_settings:
cloud_sql_instances: [project:region:instance]
I have tried adding =tcp:5432 with all variations of the above dbhost
Errors:
In the logs from the app engine in the cloud console, connecting provides only the following information:
sql: database is closed
As I understand, this means that no connection could be created to the database.
This error matches the error I get when running the code locally from any machine that hasn't had its IP address added as an authorized network from the postgreSQL instance.
Formalized Question:
Given the above, what code, options, settings, etc. do I need to add or change in order to successfully connect from the app engine flex deployment to the cloud SQL db?
If I had access to the project where the postgres Cloud SQL instance is, is there anything in specific I could do to ensure the connection?
Thank you.

Answer 1

my apologies for answering my own question.
Over the weekend I was able to solve this problem. After badgering for a double check, it turned out that the Cloud SQL instance was not set up with a private IP Address (so the assurances to me about the instance being set up correctly, and my own assurances in the question, were false).
A new Cloud SQL Instance had to be created and assigned a private IP address, as the documentation is very clear in stating that an existing Cloud SQL instance cannot be assigned a private IP address once created without one.
The App Engine Flex deploy was able to connect using the private IP address without incident.
Sorry again!