Add option to use http.Header.Set when setting headers in Go client (#24791)

* add option to use http.Header.Set when setting headers in go client

* upadte samples

* update tests

* use tabs

* update tests

Author: wing328

docs/generators/go.md

@@ -31,6 +31,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |structPrefix|whether to prefix struct with the class name. e.g. DeletePetOpts => PetApiDeletePetOpts| |false|
 |useDefaultValuesForRequiredVars|Use default values for required variables when available| |false|
+|useHttpHeaderSet|When setting HTTP request headers, use http.Header.Set with canonicalized header names| |false|
 |useOneOfDiscriminatorLookup|Use the discriminator's mapping in oneOf to speed up the model lookup. IMPORTANT: Validation (e.g. one and only one match in oneOf's schemas) will be skipped.| |false|
 |withAWSV4Signature|whether to include AWS v4 signature support| |false|
 |withGoMod|Generate go.mod and go.sum| |true|

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

@@ -63,6 +63,8 @@ public abstract class AbstractGoCodegen extends DefaultCodegen implements Codege
     protected boolean generateUnmarshalJSON = true;
     @Setter
     protected boolean useDefaultValuesForRequiredVars = false;
+    @Setter
+    protected boolean useHttpHeaderSet = false;
 
     @Setter
     protected String packageName = "openapi";

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

@@ -65,6 +65,7 @@ public class GoClientCodegen extends AbstractGoCodegen {
     public static final String MODEL_FILE_FOLDER = "modelFileFolder";
     public static final String WITH_GO_MOD = "withGoMod";
     public static final String USE_DEFAULT_VALUES_FOR_REQUIRED_VARS = "useDefaultValuesForRequiredVars";
+    public static final String USE_HTTP_HEADER_SET = "useHttpHeaderSet";
     public static final String IMPORT_VALIDATOR = "importValidator";
     @Setter protected String goImportAlias = "openapiclient";
     protected boolean isGoSubmodule = false;
@@ -138,6 +139,7 @@ public GoClientCodegen() {
         cliOptions.add(CliOption.newBoolean(WITH_AWSV4_SIGNATURE, "whether to include AWS v4 signature support"));
         cliOptions.add(CliOption.newBoolean(GENERATE_INTERFACES, "Generate interfaces for api classes"));
         cliOptions.add(CliOption.newBoolean(USE_DEFAULT_VALUES_FOR_REQUIRED_VARS, "Use default values for required variables when available"));
+        cliOptions.add(CliOption.newBoolean(USE_HTTP_HEADER_SET, "When setting HTTP request headers, use http.Header.Set with canonicalized header names"));
 
         // option to change the order of form/body parameter
         cliOptions.add(CliOption.newBoolean(
@@ -276,6 +278,11 @@ public void processOpts() {
             additionalProperties.put(USE_DEFAULT_VALUES_FOR_REQUIRED_VARS, useDefaultValuesForRequiredVars);
         }
 
+        if (additionalProperties.containsKey(USE_HTTP_HEADER_SET)) {
+            setUseHttpHeaderSet(Boolean.parseBoolean(additionalProperties.get(USE_HTTP_HEADER_SET).toString()));
+            additionalProperties.put(USE_HTTP_HEADER_SET, useHttpHeaderSet);
+        }
+
         // Generate the 'signing.py' module, but only if the 'HTTP signature' security scheme is specified in the OAS.
         Map<String, SecurityScheme> securitySchemeMap = openAPI != null ?
                 (openAPI.getComponents() != null ? openAPI.getComponents().getSecuritySchemes() : null) : null;

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

@@ -416,7 +416,12 @@ func (c *APIClient) prepareRequest(
 	if len(headerParams) > 0 {
 		headers := http.Header{}
 		for h, v := range headerParams {
+			{{#useHttpHeaderSet}}
 			headers.Set(h, v)
+			{{/useHttpHeaderSet}}
+			{{^useHttpHeaderSet}}
+			headers[h] = []string{v}
+			{{/useHttpHeaderSet}}
 		}
 		localVarRequest.Header = headers
 	}

modules/openapi-generator/src/test/java/org/openapitools/codegen/go/GoClientOptionsTest.java

@@ -56,5 +56,7 @@ protected void verifyOptions() {
         verify(clientCodegen).setGenerateUnmarshalJSON(GoClientOptionsProvider.GENERATE_UNMARSHAL_JSON_VALUE);
         verify(clientCodegen).setUseDefaultValuesForRequiredVars(GoClientOptionsProvider.USE_DEFAULT_VALUES_FOR_REQUIRED_VARS_VALUE);
         verify(clientCodegen).setEnumUnknownDefaultCase(Boolean.parseBoolean(GoClientOptionsProvider.ENUM_UNKNOWN_DEFAULT_CASE_VALUE));
+        verify(clientCodegen).setUseHttpHeaderSet(GoClientOptionsProvider.USE_HTTP_HEADER_SET);
+
     }
 }

modules/openapi-generator/src/test/java/org/openapitools/codegen/options/GoClientOptionsProvider.java

@@ -41,6 +41,8 @@ public class GoClientOptionsProvider implements OptionsProvider {
     public static final boolean GENERATE_UNMARSHAL_JSON_VALUE = true;
     public static final boolean USE_DEFAULT_VALUES_FOR_REQUIRED_VARS_VALUE = true;
     public static final String ENUM_UNKNOWN_DEFAULT_CASE_VALUE = "false";
+    public static final boolean USE_HTTP_HEADER_SET = true;
+
 
     @Override
     public String getLanguage() {
@@ -68,6 +70,7 @@ public Map<String, String> createOptions() {
                 .put("structPrefix", "true")
                 .put(CodegenConstants.USE_DEFAULT_VALUES_FOR_REQUIRED_VARS, "true")
                 .put(CodegenConstants.ENUM_UNKNOWN_DEFAULT_CASE, ENUM_UNKNOWN_DEFAULT_CASE_VALUE)
+                .put("useHttpHeaderSet", "true")
                 .build();
     }