try upgrading sample version

try upgrading sample version of adapter dependency

Restore GSON mapper preference

default to GSON if impl not specified

spring-cloud-function-adapters/spring-cloud-function-adapter-gcp/src/main/java/org/springframework/cloud/function/adapter/gcp/FunctionInvoker.java

@@ -66,6 +66,12 @@ public class FunctionInvoker extends AbstractSpringFunctionAdapterInitializer<Ht
 		if (System.getenv().containsKey("spring.cloud.function.definition")) {
 			this.functionName = System.getenv("spring.cloud.function.definition");
 		}
+
+		// Default to GSON if implementation not specified.
+		if (!System.getenv().containsKey("spring.http.converters.preferred-json-mapper")) {
+			System.setProperty("spring.http.converters.preferred-json-mapper", "gson");
+		}
+
 		Thread.currentThread() // TODO: remove after upgrading to 1.0.0-alpha-2-rc5
 				.setContextClassLoader(FunctionInvoker.class.getClassLoader());
 		initialize(null);

spring-cloud-function-samples/function-sample-gcp-http/pom.xml

@@ -23,7 +23,7 @@
 		<dependency>
 			<groupId>org.springframework.cloud</groupId>
 			<artifactId>spring-cloud-function-adapter-gcp</artifactId>
-			<version>3.1.2-SNAPSHOT</version>
+			<version>3.1.3-SNAPSHOT</version>
 		</dependency>
 
 		<!-- test dependencies -->
@@ -74,7 +74,7 @@
 					<dependency>
 						<groupId>org.springframework.cloud</groupId>
 						<artifactId>spring-cloud-function-adapter-gcp</artifactId>
-						<version>3.1.0-SNAPSHOT</version>
+						<version>3.1.3-SNAPSHOT</version>
 					</dependency>
 				</dependencies>
 			</plugin>