title: How to define an optional parameter in path using swagger
body: <p>There is a function in my REST web service working with GET method and it has two optional parameters. </p>
  
  <p>I tried to define it in Swagger but I encountered an error, <strong>Not a valid parameter definition</strong>, after I set the <code>required</code> as <code>false</code>.</p>
  
  <p>I found out that if I set the <code>required</code> value as <code>true</code> the error will be gone. Here is a sample of my Swagger code.</p>
  
  <pre><code>...
  paths:
    '/get/{param1}/{param2}':
      get:
        ...
        parameters:
        - name: param1
          in: path
          description: 'description regarding param1'
          required: false
          type: string
        - name: param2
          in: path
          description: 'description regarding param2'
          required: false
          type: string
  </code></pre>
  
  <p>I didn't experience this with parameters in body or the the ones in query. I think this problem is only related to parameters in path. I could not find any solution in swagger specification files either. </p>
  
  <p>Is there any other way to define optional parameters in Swagger or do I have any mistake in my code?</p>
  
  <p>Any help would be appreciated.</p>