Postgresql – How to use non-blocking connection function in libpq and trigger a notification or callback when the connection is established withlibpq — C Library?

I am trying to establish a non-blocking connection to a PostgreSQL database using the libpq library in C, and I want to be able to trigger a notification or callback function once the connection is established.

I know that PQconnectStart() can be used to initiate a non-blocking connection and that PQconnectPoll() can be used to check the status of the connection, but I’m not sure how to trigger a notification or callback function once the connection is established.

PGconn *conn;
PGconnStatusType status;

conn = PQconnectStart("dbname=mydatabase user=myusername password=mypassword");

if (conn == NULL) {
    fprintf(stderr, "Connection initialization failedn");
    exit(1);
}

while ((status = PQconnectPoll(conn)) != CONNECTION_OK) {
    if (status == PGRES_POLLING_FAILED) {
        fprintf(stderr, "Connection failed: %sn", PQerrorMessage(conn));
        PQfinish(conn);
        exit(1);
    }
}

// Connection is established, how do I trigger a notification or callback function?

// Do something with the connection here...

PQfinish(conn);