GP-5514 fix hard coded struct field ordinal for golang 1.23+

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/golang/rtti/types/GoInterfaceType.java

@@ -112,7 +112,9 @@ public class GoInterfaceType extends GoType {
 		StructureDataType itabStruct = new StructureDataType(ifaceCP, ifaceName + "_itab", 0, dtm);
 		itabStruct.replaceWith(genericItabStruct);
 
-		int funDTCOrdinal = 4; // a bit of a hack, could also lookup by name "Fun"
+		FieldMappingInfo<GoItab> funFMI =
+			programContext.getStructureMappingInfo(GoItab.class).getFieldInfo("fun");
+		int funDTCOrdinal = funFMI.getDtc().getOrdinal();
 		//DataTypeComponentImpl funDtc = itabStruct.getComponent(funDTCOrdinal);
 		itabStruct.delete(funDTCOrdinal);
 

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/golang/structmapping/StructureMappingInfo.java

@@ -130,6 +130,15 @@ public class StructureMappingInfo<T> {
 		return fields;
 	}
 
+	public FieldMappingInfo<T> getFieldInfo(String javaFieldName) throws IOException {
+		for (FieldMappingInfo<T> fmi : fields) {
+			if (fmi.getField().getName().equals(javaFieldName)) {
+				return fmi;
+			}
+		}
+		throw new IOException("Java field name not found: " + javaFieldName);
+	}
+
 	public List<Method> getAfterMethods() {
 		return afterMethods;
 	}