[Go][Experimental] better oneOf and anyOf implementation (#6166)

* diff oneOf implementation

* update oas3 samples

* fix imports

* remove commented code

Author: wing328

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java

@@ -42,7 +42,6 @@ public GoClientExperimentalCodegen() {
         embeddedTemplateDir = templateDir = "go-experimental";
 
         usesOptionals = false;
-        useOneOfInterfaces = true;
 
         generatorMetadata = GeneratorMetadata.newBuilder(generatorMetadata).stability(Stability.EXPERIMENTAL).build();
     }
@@ -167,6 +166,8 @@ public Map<String, Object> postProcessModels(Map<String, Object> objs) {
         // must be invoked at the beginning of this method.
         objs = super.postProcessModels(objs);
 
+        List<Map<String, String>> imports = (List<Map<String, String>>) objs.get("imports");
+
         List<Map<String, Object>> models = (List<Map<String, Object>>) objs.get("models");
         for (Map<String, Object> m : models) {
             Object v = m.get("model");
@@ -193,21 +194,22 @@ public Map<String, Object> postProcessModels(Map<String, Object> objs) {
                                 + param.dataType.substring(1);
                     }
                 }
-            }
-        }
-        return objs;
-    }
 
-    @Override
-    public void addImportsToOneOfInterface(List<Map<String, String>> imports) {
-        for (String i : Arrays.asList("fmt")) {
-            Map<String, String> oneImport = new HashMap<String, String>() {{
-                put("import", i);
-            }};
-            if (!imports.contains(oneImport)) {
-                imports.add(oneImport);
+                // additional import for different cases
+                // oneOf
+                if (model.oneOf != null && !model.oneOf.isEmpty()) {
+                    imports.add(createMapping("import", "fmt"));
+                }
+
+                // anyOf
+                if (model.anyOf != null && !model.anyOf.isEmpty()) {
+                    imports.add(createMapping("import", "fmt"));
+                }
             }
+
+
         }
+        return objs;
     }
 
     @Override
@@ -262,7 +264,7 @@ private String constructExampleCode(CodegenParameter codegenParameter, HashMap<S
                 return "URL(string: \"https://example.com\")!";
             } else if (codegenParameter.isDateTime || codegenParameter.isDate) { // datetime or date
                 return "Get-Date";
-            } else{ // numeric
+            } else { // numeric
                 if (StringUtils.isEmpty(codegenParameter.example)) {
                     return codegenParameter.example;
                 } else {
@@ -302,7 +304,7 @@ private String constructExampleCode(CodegenProperty codegenProperty, HashMap<Str
                 return "\"https://example.com\")!";
             } else if (codegenProperty.isDateTime || codegenProperty.isDate) { // datetime or date
                 return "time.Now()";
-            } else{ // numeric
+            } else { // numeric
                 String example;
                 if (StringUtils.isEmpty(codegenProperty.example)) {
                     example = codegenProperty.example;

modules/openapi-generator/src/main/resources/go-experimental/client.mustache

@@ -169,7 +169,7 @@ func (c *APIClient) callAPI(request *http.Request) (*http.Response, error) {
 			return nil, err
 		}
 		log.Printf("\n%s\n", string(dump))
-        }
+	}
 
 	resp, err := c.cfg.HTTPClient.Do(request)
 	if err != nil {
@@ -381,7 +381,15 @@ func (c *APIClient) decode(v interface{}, b []byte, contentType string) (err err
 		return nil
 	}
 	if jsonCheck.MatchString(contentType) {
-		if err = json.Unmarshal(b, v); err != nil {
+		if actualObj, ok := v.(interface{GetActualInstance() interface{}}); ok { // oneOf, anyOf schemas
+			if unmarshalObj, ok := actualObj.(interface{UnmarshalJSON([]byte) error}); ok { // make sure it has UnmarshalJSON defined
+				if err = unmarshalObj.UnmarshalJSON(b); err!= nil {
+					return err
+				}
+			} else {
+				errors.New("Unknown type with GetActualInstance but no unmarshalObj.UnmarshalJSON defined")
+			}
+		} else if err = json.Unmarshal(b, v); err != nil { // simple model
 			return err
 		}
 		return nil