Merge pull request #31 in FEE/akamaiopen-edgegrid-golang from TFP-168-add-env-fallback to v2

* commit 'ed89b39bf9779c795b4e90e96e18aa02534682e2':
  make edgerc.WithEnv explicit fallback to files so existing provider use does not break
  make edgerc.WithEnv fallback to files so existing provider use does not break
  make edgerc.WithEnv fallback to files so existing provider use does not break

Author: piotrpio

pkg/edgegrid/config.go

@@ -59,7 +59,6 @@ type (
 // New returns new configuration with the specified options
 func New(opts ...Option) (*Config, error) {
 	c := &Config{
-		file:    DefaultConfigFile,
 		section: DefaultSection,
 		env:     false,
 	}
@@ -69,14 +68,17 @@ func New(opts ...Option) (*Config, error) {
 	}
 
 	if c.env {
-		if err := c.FromEnv(c.section); err != nil {
-			return c, err
+		if err := c.FromEnv(c.section); err == nil {
+			return c, nil
+		} else if !errors.Is(err, ErrRequiredOptionEnv) {
+			return nil, err
 		}
-		return c, nil
 	}
 
-	if err := c.FromFile(c.file, c.section); err != nil {
-		return c, fmt.Errorf("unable to load config from environment or .edgerc file: %w", err)
+	if c.file != "" {
+		if err := c.FromFile(c.file, c.section); err != nil {
+			return c, fmt.Errorf("unable to load config from environment or .edgerc file: %w", err)
+		}
 	}
 
 	return c, nil