Google Cloud Functions Datastore Emulator local connection with functions - google-cloud-datastore

Question

I've launched the local Datastore emulator and although wrote and test GCF with the remote Datastore instance (not emulated one). Now I'm trying to use the locally launched Datastore instance for testing purposes, but all requests still going to the cloud instance of Datastore.
Here is the code.
const db = require("#google-cloud/datastore")();
exports.signUp = (req, res) => {
if(!req.body.firstName || !req.body.lastName || !req.body.email) {
res.status(400).send("Incorrect user data passed");
} else {
let key = db.key("User");
console.log("KEY: ", key);
db.insert({
key: key,
data: {
firsName: req.body.firsName,
lastName: req.body.lastName,
email: req.body.email
}
}, (err, apiResponse) => {
console.log(apiResponse);
if(err) {
res.status(400).json({
message: "Error occured during creation"
});
} else {
res.status(200).json({
message: `Created under ${apiResponse}`
});
}
});
}
};
I know about the apiEndpoint (link on documentation) parameter in the Datastore instance configuration object. But should it actually be passed explicitly in the code? I though that there should be some environment variable that will tell default configuration to search for the Datastore emulator first, and then try to use the cloud one.