https://github.com/poutsma/web-function-sample/blob/master/pom.xml https://github.com/making/demo-lambda-routing/blob/master/src/main/java/com/example/DemoLambdaRoutingApplication.java
method 指定が間違ってると method not allowed じゃなくて not found 返すなw
reactive だよう https://github.com/bclozel/spring-boot-web-reactive/tree/master/spring-boot-sample-web-reactive