Google Compute Engine无法将我的Go应用连接到PostgreSQL基础

I work on an application written in Go which uses a PostgreSQL database. I am deploying that app on Google Cloud Platform, for which I chose the Compute Engine service.

I created 2 instances: an instance for running the application and another for the database server. The OS of both instances is Ubuntu 18.04.

When I test the application locally, everything works as expected. Specifically, there are no problems connecting the app with the database.

When I try to run the app on Compute Engine, I get this error:

panic: dial tcp 10.132.0.4:5432: connect: connection refused
    goroutine 1 [running]:
main.init.0()
    /home/gauthier/gocode/sprint0/main.go:29 +0x113
exit status 2

Here's some information about my VMs:

-VM1(go)

Internal IP: 10.132.0.3
External IP: 35.205.41.152

-VM2(postgreSQL)

Internal IP: 10.132.0.4
External IP: 35.241.174.119

In my app, I connect to the database like this

var db *sql.DB

func init() {
    var err error
    db, err =sql.Open("postgres","postgres://postgres:postgres@10.132.0.4/quotes?sslmode=disable")
    if err != nil {
        panic(err)
    }

    if err = db.Ping(); err != nil {
        panic(err)
    }
    fmt.Println("You connected to your database")
}

I cannot find anything in the GCP documentation which fixes this issue.