Revert "Change defaults when generating a client via smithy CLI (#558)" (#559)

This reverts commit 95ba318.

This feature may interact in unexpected ways with existing SDK codegen, so while we figure it out we'll roll back these changes. They will be re-applied later

Author: Madrigal

codegen/smithy-go-codegen-test/smithy-build.json

@@ -6,14 +6,14 @@
             "module": "github.com/aws/smithy-go/internal/tests/service/weather",
             "moduleVersion": "0.0.1",
             "generateGoMod": true,
-            "goDirective": "1.21"
+            "goDirective": "1.18"
         },
         "go-server-codegen": {
             "service": "example.weather#Weather",
             "module": "github.com/aws/smithy-go/internal/tests/server/weather",
             "moduleVersion": "0.0.1",
             "generateGoMod": true,
-            "goDirective": "1.21"
+            "goDirective": "1.18"
         }
     }
 }

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/GoModuleInfo.java

@@ -27,7 +27,7 @@
 
 public final class GoModuleInfo {
 
-    public static final String DEFAULT_GO_DIRECTIVE = "1.21";
+    public static final String DEFAULT_GO_DIRECTIVE = "1.15";
 
     private List<SymbolDependency> dependencies;
 

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/GoSettings.java

@@ -92,7 +92,7 @@ public static GoSettings from(ObjectNode config, ArtifactType artifactType) {
         settings.setModuleDescription(config.getStringMemberOrDefault(
                 MODULE_DESCRIPTION, settings.getModuleName() + " client"));
         settings.setModuleVersion(config.getStringMemberOrDefault(MODULE_VERSION, null));
-        settings.setGenerateGoMod(config.getBooleanMemberOrDefault(GENERATE_GO_MOD, true));
+        settings.setGenerateGoMod(config.getBooleanMemberOrDefault(GENERATE_GO_MOD, false));
         settings.setGoDirective(config.getStringMemberOrDefault(GO_DIRECTIVE, GoModuleInfo.DEFAULT_GO_DIRECTIVE));
         return settings;
     }