Create a go lang firestore test connection with custom JWT claims

example.go

package main

type TestingToken struct {
	jwt string
}

func (t token) GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error) {
	return map[string]string{
		"authorization": "bearer " + t.token,
	}, nil
}

func (t token) RequireTransportSecurity() bool {
	return false
}

func createInsecureJWT(uid, role string) TestingToken {
	header := `{"alg":"none","kid":"fakekid","typ":"JWT"}`
	body := fmt.Sprintf(`{"iat":%d,"eat":%d,"sub":"%s","uid":"%s","role":"%s"}`, time.Now().Unix(), time.Now().Unix()+10000, uid, uid, role)

	jwt := fmt.Sprintf(
		"%s.%s.%s",
		base64.RawURLEncoding.EncodeToString([]byte(header)),
		base64.RawURLEncoding.EncodeToString([]byte(body)),
		"",
	)

	return TestingToken{jwt: t}
}

func getClient() *firestore.Client {
	ctx := context.Background()

	token := createInsecureJWT("ab", "admin")
	conn, err := grpc.Dial(
		os.Getenv("FIRESTORE_EMULATOR_HOST"),
		grpc.WithInsecure(),
		grpc.WithPerRPCCredentials(token),
	)
	if err != nil {
		log.Fatal(err)
	}
	client, err := firestore.NewClient(
		ctx,
		"testproject",
		option.WithGRPCConn(conn),
	)
	if err != nil {
		log.Fatal(err)
	}

	return client
}