diff --git a/circle.yml b/circle.yml
index 04eb415803bc..78ebec264186 100644
--- a/circle.yml
+++ b/circle.yml
@@ -22,9 +22,9 @@ jobs:
     - restore_cache:
         keys:
         # Default branch if not
-        - source-v1-{{ .Branch }}-{{ .Revision }}
-        - source-v1-{{ .Branch }}-
-        - source-v1-
+        - source-v2-{{ .Branch }}-{{ .Revision }}
+        - source-v2-{{ .Branch }}-
+        - source-v2-
     # Machine Setup
     #   If you break your build into multiple jobs with workflows, you will probably want to do the parts of this that are relevant in each
     # The following `checkout` command checks out your code to your working directory. In 1.0 we did this implicitly. In 2.0 you can choose where in the course of a job your code should be checked out.
@@ -70,7 +70,7 @@ jobs:
     - run: ./CI/circle_parallel.sh 
     # Save dependency cache
     - save_cache:
-        key: source-v1-{{ .Branch }}-{{ .Revision }}
+        key: source-v2-{{ .Branch }}-{{ .Revision }}
         paths:
         # This is a broad list of cache paths to include many possible development environments
         # You can probably delete some of these entries
diff --git a/docs/generators/go-experimental.md b/docs/generators/go-experimental.md
index 80e9630d6a2f..e4c738c0e3c7 100644
--- a/docs/generators/go-experimental.md
+++ b/docs/generators/go-experimental.md
@@ -5,6 +5,7 @@ sidebar_label: go-experimental
 
 | Option | Description | Values | Default |
 | ------ | ----------- | ------ | ------- |
+|disallowAdditionalPropertiesIfNotPresent|Specify the behavior when the 'additionalProperties' keyword is not present in the OAS document. If false: the 'additionalProperties' implementation is compliant with the OAS and JSON schema specifications. If true: when the 'additionalProperties' keyword is not present in a schema, the value of 'additionalProperties' is set to false, i.e. no additional properties are allowed. Note: this mode is not compliant with the JSON schema specification. This is the original openapi-generator behavior.This setting is currently ignored for OAS 2.0 documents:  1) When the 'additionalProperties' keyword is not present in a 2.0 schema, additional properties are NOT allowed.  2) Boolean values of the 'additionalProperties' keyword are ignored. It's as if additional properties are NOT allowed.Note: the root cause are issues #1369 and #1371, which must be resolved in the swagger-parser project.|<dl><dt>**false**</dt><dd>The 'additionalProperties' implementation is compliant with the OAS and JSON schema specifications.</dd><dt>**true**</dt><dd>when the 'additionalProperties' keyword is not present in a schema, the value of 'additionalProperties' is automatically set to false, i.e. no additional properties are allowed. Note: this mode is not compliant with the JSON schema specification. This is the original openapi-generator behavior.</dd></dl>|true|
 |enumClassPrefix|Prefix enum with class name| |false|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |isGoSubmodule|whether the generated Go module is a submodule| |false|
diff --git a/modules/openapi-generator-maven-plugin/examples/spring.xml b/modules/openapi-generator-maven-plugin/examples/spring.xml
index a0654ffe260d..2befe89eb0ac 100644
--- a/modules/openapi-generator-maven-plugin/examples/spring.xml
+++ b/modules/openapi-generator-maven-plugin/examples/spring.xml
@@ -20,7 +20,7 @@
 				<groupId>org.openapitools</groupId>
 				<artifactId>openapi-generator-maven-plugin</artifactId>
 				<!-- RELEASE_VERSION -->
-				<version>4.3.1-SNAPSHOT</version>
+				<version>5.0.0-SNAPSHOT</version>
 				<!-- /RELEASE_VERSION -->
 				<executions>
 					<execution>
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index 1ee020cee2bb..fd949a0e9a9d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -2514,7 +2514,11 @@ public class DefaultCodegen implements CodegenConfig {
 
         // process 'additionalProperties'
         if (schema.getAdditionalProperties() == null) {
-            m.isAdditionalPropertiesTrue = false; // TODO fix the old (incorrect) behaviour (likely with an option)
+            if (disallowAdditionalPropertiesIfNotPresent) {
+                m.isAdditionalPropertiesTrue = false;
+            } else {
+                m.isAdditionalPropertiesTrue = true;
+            }
         } else if (schema.getAdditionalProperties() instanceof Boolean) {
             if (Boolean.TRUE.equals(schema.getAdditionalProperties())) {
                 m.isAdditionalPropertiesTrue = true;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
index c52e87e65afc..a5434dedf139 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
@@ -47,6 +47,21 @@ public class GoClientExperimentalCodegen extends GoClientCodegen {
         generatorMetadata = GeneratorMetadata.newBuilder(generatorMetadata).stability(Stability.EXPERIMENTAL).build();
 
         cliOptions.add(new CliOption(CodegenConstants.USE_ONEOF_DISCRIMINATOR_LOOKUP, CodegenConstants.USE_ONEOF_DISCRIMINATOR_LOOKUP_DESC).defaultValue("false"));
+        // option to change how we process + set the data in the 'additionalProperties' keyword.
+        CliOption disallowAdditionalPropertiesIfNotPresentOpt = CliOption.newBoolean(
+                CodegenConstants.DISALLOW_ADDITIONAL_PROPERTIES_IF_NOT_PRESENT,
+                CodegenConstants.DISALLOW_ADDITIONAL_PROPERTIES_IF_NOT_PRESENT_DESC).defaultValue(Boolean.TRUE.toString());
+        Map<String, String> disallowAdditionalPropertiesIfNotPresentOpts = new HashMap<>();
+        disallowAdditionalPropertiesIfNotPresentOpts.put("false",
+                "The 'additionalProperties' implementation is compliant with the OAS and JSON schema specifications.");
+        disallowAdditionalPropertiesIfNotPresentOpts.put("true",
+                "when the 'additionalProperties' keyword is not present in a schema, " +
+                        "the value of 'additionalProperties' is automatically set to false, i.e. no additional properties are allowed. " +
+                        "Note: this mode is not compliant with the JSON schema specification. " +
+                        "This is the original openapi-generator behavior.");
+        disallowAdditionalPropertiesIfNotPresentOpt.setEnum(disallowAdditionalPropertiesIfNotPresentOpts);
+        cliOptions.add(disallowAdditionalPropertiesIfNotPresentOpt);
+        this.setDisallowAdditionalPropertiesIfNotPresent(true);
     }
 
     /**
@@ -102,6 +117,11 @@ public class GoClientExperimentalCodegen extends GoClientCodegen {
             additionalProperties.put(CodegenConstants.USE_ONEOF_DISCRIMINATOR_LOOKUP, useOneOfDiscriminatorLookup);
         }
 
+        if (additionalProperties.containsKey(CodegenConstants.DISALLOW_ADDITIONAL_PROPERTIES_IF_NOT_PRESENT)) {
+            this.setDisallowAdditionalPropertiesIfNotPresent(Boolean.valueOf(additionalProperties
+                    .get(CodegenConstants.DISALLOW_ADDITIONAL_PROPERTIES_IF_NOT_PRESENT).toString()));
+        }
+
     }
 
     public void setUseOneOfDiscriminatorLookup(boolean useOneOfDiscriminatorLookup) {