set default library in order to fix issue.

Author: HugoMario

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/KotlinServerCodegen.java

@@ -4,9 +4,16 @@
 import com.samskivert.mustache.Mustache;
 import io.swagger.codegen.CliOption;
 import io.swagger.codegen.CodegenConstants;
+import io.swagger.codegen.CodegenModel;
+import io.swagger.codegen.CodegenOperation;
 import io.swagger.codegen.CodegenType;
 import io.swagger.codegen.SupportingFile;
 import io.swagger.codegen.mustache.*;
+import io.swagger.models.ArrayModel;
+import io.swagger.models.Model;
+import io.swagger.models.Operation;
+import io.swagger.models.Swagger;
+import io.swagger.models.parameters.Parameter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -15,10 +22,14 @@
 import java.util.List;
 import java.util.Map;
 
+import static io.swagger.codegen.CodegenConstants.GENERATE_APIS;
+
 public class KotlinServerCodegen extends AbstractKotlinCodegen {
 
     public static final String DEFAULT_LIBRARY = Constants.KTOR;
-    static Logger LOGGER = LoggerFactory.getLogger(KotlinServerCodegen.class);
+    public static final String GENERATE_APIS = "generateApis";
+
+    private static Logger LOGGER = LoggerFactory.getLogger(KotlinServerCodegen.class);
     private Boolean autoHeadFeatureEnabled = true;
     private Boolean conditionalHeadersFeatureEnabled = false;
     private Boolean hstsFeatureEnabled = true;
@@ -123,8 +134,14 @@ public CodegenType getTag() {
     public void processOpts() {
         super.processOpts();
 
+        if (!additionalProperties.containsKey(GENERATE_APIS)) {
+            additionalProperties.put(GENERATE_APIS, true);
+        }
+
         if (additionalProperties.containsKey(CodegenConstants.LIBRARY)) {
             this.setLibrary((String) additionalProperties.get(CodegenConstants.LIBRARY));
+        } else {
+            this.setLibrary(DEFAULT_LIBRARY);
         }
 
         if (additionalProperties.containsKey(Constants.AUTOMATIC_HEAD_REQUESTS)) {
@@ -157,9 +174,9 @@ public void processOpts() {
             additionalProperties.put(Constants.COMPRESSION, getCompressionFeatureEnabled());
         }
 
-        Boolean generateApis = additionalProperties.containsKey(CodegenConstants.GENERATE_APIS) && (Boolean)additionalProperties.get(CodegenConstants.GENERATE_APIS);
         String packageFolder = (sourceFolder + File.separator + packageName).replace(".", File.separator);
         String resourcesFolder = "src/main/resources"; // not sure this can be user configurable.
+        Boolean generateApis = additionalProperties.containsKey(GENERATE_APIS) && (Boolean)additionalProperties.get(GENERATE_APIS);
 
         supportingFiles.add(new SupportingFile("README.mustache", "", "README.md"));
         supportingFiles.add(new SupportingFile("Dockerfile.mustache", "", "Dockerfile"));