Merge pull request #6 from LampardNguyen234/dev/init-without-credentials

chore(gcp): allow to init server without a credential file

gcpkms/README.md

@@ -19,7 +19,7 @@ KMS key in GCP. To do this, please follow the instruction [here](https://cloud.g
 Remember to choose `Purpose = Asymmetric sign` and `Algorithm = Elliptic Curve secp256k1 - SHA256 Digest` in the 
 `Create key` screen. 
 
-### Download Credential
+### Download Credential (Optional)
 Head over [the `IAM` page of the GCP](https://cloud.google.com/iam/docs/service-accounts), create a service account to use to API and download the credential.
 The credential file looks like the following:
 ```json

gcpkms/config.go

@@ -58,10 +58,6 @@ func (cfg Config) IsValid() (bool, error) {
 		return false, fmt.Errorf("empty LocationID")
 	}
 
-	if cfg.CredentialLocation == "" {
-		return false, fmt.Errorf("empty CredentialLocation")
-	}
-
 	if !cfg.Key.isValid() {
 		return false, fmt.Errorf("invalid Key")
 	}

gcpkms/signer.go

@@ -38,7 +38,11 @@ func NewGoogleKMSClient(ctx context.Context, cfg Config, txSigner ...types.Signe
 	if _, err := cfg.IsValid(); err != nil {
 		return nil, fmt.Errorf("invalid config")
 	}
-	client, err := kms.NewKeyManagementClient(ctx, option.WithCredentialsFile(cfg.CredentialLocation))
+	options := make([]option.ClientOption, 0)
+	if cfg.CredentialLocation != "" {
+		options = append(options, option.WithCredentialsFile(cfg.CredentialLocation))
+	}
+	client, err := kms.NewKeyManagementClient(ctx, options...)
 	if err != nil {
 		return nil, err
 	}