feat: added func to load session token

pkg/auth/auth.go

@@ -12,6 +12,9 @@ import (
 // fails with one options, it will fallback to the next option until
 // all options are exhausted.
 //
+// NOTE: Access tokens expire after a set period. Inspect the token
+// and check the `exp` claim to see if the token is expired.
+//
 // Returns a token as a string with no error if successful.
 // Alternatively, returns an empty string with an error if a token is
 // not able to be loaded.
@@ -33,5 +36,38 @@ func LoadAccessToken(path string) (string, error) {
 	if testToken != "" {
 		return testToken, nil
 	}
-	return "", fmt.Errorf("failed to load token from environment variable, file, or config")
+	return "", fmt.Errorf("failed to load access token from environment variable, file, or config")
+}
+
+// LoadSessionToken() behaves similarly to LoadAccessToken() by
+// trying to load a session token for BMC authentication. Session
+// authentication is preferred over using basic authentication to
+// reduce the overhead caused by performing a login. This method
+// tries to load from an SESSION_TOKEN environment variable first,
+// then a file specified by the path, then from the "access-token"
+// property in the config file.
+//
+// NOTE: Like access tokens, session tokens expired after a given
+// time period if not used.
+//
+// Returns a session token as a string with no error if successful.
+func LoadSessionToken(path string) (string, error) {
+	// try to load token from env var
+	testToken := os.Getenv("SESSION_TOKEN")
+	if testToken != "" {
+		return testToken, nil
+	}
+
+	// try reading access token from a file
+	b, err := os.ReadFile(path)
+	if err == nil {
+		return string(b), nil
+	}
+
+	// TODO: try to load token from config
+	testToken = viper.GetString("session-token")
+	if testToken != "" {
+		return testToken, nil
+	}
+	return "", fmt.Errorf("failed to load session token from environment variable, file, or config")
 }