[Golang] Allow retrieving the underlying configuration for APIClient (#3976)

* Allow retrieving the underlying configuration for APIClient

  - Needed for dynamically changing the underlying implementations and
    for testing
  - Fixes #1321 and #3412

* Added go-petstore-withXml changes suggested by circleci

* Add caution note about modifying configuration while live

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

@@ -169,6 +169,12 @@ func (c *APIClient) ChangeBasePath(path string) {
 	c.cfg.BasePath = path
 }
 
+// Allow modification of underlying config for alternate implementations and testing
+// Caution: modifying the configuration while live can cause data races and potentially unwanted behavior
+func (c *APIClient) GetConfig() *Configuration {
+	return c.cfg
+}
+
 // prepareRequest build the request
 func (c *APIClient) prepareRequest(
 	ctx context.Context,

samples/client/petstore/go/go-petstore-withXml/client.go

@@ -181,6 +181,12 @@ func (c *APIClient) ChangeBasePath(path string) {
 	c.cfg.BasePath = path
 }
 
+// Allow modification of underlying config for alternate implementations and testing
+// Caution: modifying the configuration while live can cause data races and potentially unwanted behavior
+func (c *APIClient) GetConfig() *Configuration {
+	return c.cfg
+}
+
 // prepareRequest build the request
 func (c *APIClient) prepareRequest(
 	ctx context.Context,

samples/client/petstore/go/go-petstore/client.go

@@ -180,6 +180,12 @@ func (c *APIClient) ChangeBasePath(path string) {
 	c.cfg.BasePath = path
 }
 
+// Allow modification of underlying config for alternate implementations and testing
+// Caution: modifying the configuration while live can cause data races and potentially unwanted behavior
+func (c *APIClient) GetConfig() *Configuration {
+	return c.cfg
+}
+
 // prepareRequest build the request
 func (c *APIClient) prepareRequest(
 	ctx context.Context,

samples/openapi3/client/petstore/go/go-petstore/client.go

@@ -183,6 +183,12 @@ func (c *APIClient) ChangeBasePath(path string) {
 	c.cfg.BasePath = path
 }
 
+// Allow modification of underlying config for alternate implementations and testing
+// Caution: modifying the configuration while live can cause data races and potentially unwanted behavior
+func (c *APIClient) GetConfig() *Configuration {
+	return c.cfg
+}
+
 // prepareRequest build the request
 func (c *APIClient) prepareRequest(
 	ctx context.Context,