Fix panic during auth scheme resolution due to region validation (#3235)

Author: wty-Bryant

.changelog/e6d8d10b65d149ada54cc82756eed535.json

@@ -1 +1 @@
-ddbac1c617ac6bea513c16923e7883b1439b2a34
+ed49224f03828a26529458a48ff56b9b0b4db45e

SMITHY_GO_CODEGEN_VERSION

@@ -97,16 +97,18 @@ private boolean isSigV4Service(Model model, ServiceShape service) {
 
     private GoWriter.Writable writeRegionResolver() {
         return goTemplate("""
-                func bindAuthParamsRegion( _ interface{}, params $P, _ interface{}, options Options) {
+                func bindAuthParamsRegion( _ interface{}, params $P, _ interface{}, options Options) error {
                     params.Region = options.Region
+                    return nil
                 }
                 """, AuthParametersGenerator.STRUCT_SYMBOL);
     }
 
     private GoWriter.Writable writeEndpointParamResolver() {
         return goTemplate("""
-                func bindAuthEndpointParams(ctx $P, params $P, input interface{}, options Options) {
-                    params.endpointParams, _ = bindEndpointParams(ctx, input, options)
+                func bindAuthEndpointParams(ctx $P, params $P, input interface{}, options Options) (err error) {
+                    params.endpointParams, err = bindEndpointParams(ctx, input, options)
+                    return
                 }
                 """, GoStdlibTypes.Context.Context, AuthParametersGenerator.STRUCT_SYMBOL);
     }

codegen/smithy-aws-go-codegen/src/main/java/software/amazon/smithy/aws/go/codegen/customization/AwsAuthResolution.java

@@ -6,7 +6,9 @@
 import software.amazon.smithy.go.codegen.GoSettings;
 import software.amazon.smithy.go.codegen.GoStdlibTypes;
 import software.amazon.smithy.go.codegen.GoWriter;
+import software.amazon.smithy.go.codegen.SmithyGoDependency;
 import software.amazon.smithy.go.codegen.SmithyGoTypes;
+import software.amazon.smithy.go.codegen.SymbolUtils;
 import software.amazon.smithy.go.codegen.integration.GoIntegration;
 import software.amazon.smithy.go.codegen.integration.RuntimeClientPlugin;
 import software.amazon.smithy.model.Model;
@@ -98,7 +100,7 @@ func bindRegion(region string) (*string, error) {
                     if region == "" {
                         return nil, nil
                     }
-                    if !$validHost:T(region) {
+                    if !$validHost:T(region, true) {
                         return nil, $error:T("invalid input region %s", region)
                     }
                 
@@ -109,7 +111,8 @@ func bindRegion(region string) (*string, error) {
                         "awsString", SdkGoTypes.Aws.String,
                         "mapFipsRegion", SdkGoTypes.Internal.Endpoints.MapFIPSRegion,
                         "error", GoStdlibTypes.Fmt.Errorf,
-                        "validHost", SmithyGoTypes.Transport.Http.ValidHostLabel
+                        "validHost", SymbolUtils.createValueSymbolBuilder("IsValidHostLabel",
+                                SmithyGoDependency.SMITHY_ENDPOINT_RULESFN).build()
                 )
         );
     }