AsyncAPI 3 request reply (HTTP) example.

asyncapi3-request-reply-http.yml

asyncapi: 3.0.0
info:
  title: Hello world using request/reply
  version: 1.0.0
  description: Hello world example using request/reply

channels:
  hello:
    address: /hello
    messages:
      hello:
        $ref: '#/components/messages/hello'
  helloResponse:
    #address: /hello
    address: null
    messages:
      helloResponse:
        $ref: '#/components/messages/helloResponse'

operations:
  hello:
    action: send
    bindings:
      http:
        method: GET
        bindingVersion: '0.2.0'
    channel: 
      $ref: '#/channels/hello'
    reply:
      channel: 
        $ref: '#/channels/helloResponse'

components:
  messages:
    hello:
      payload:
        type: 'null'
    helloResponse:
      payload:
        type: string
        const: 'Hello world!'
        additionalProperties: false