title: Value for a session is replicated between sessions
body: <p>I have a load test where a session value is set depending on the URL that I request and can be one of two options which I choose randomly. </p>
  
  <p>When I execute the test for one user, the value in the session is set successfully with a random value. </p>
  
  <p>When I add more users the value would be set randomly but also the same for all the sessions of all users (so all users have the same session value)</p>
  
  <p>My load test looks like this</p>
  
  <pre><code>class test extends Simulation {
    val customer_types = Array("P", "B")
  
    val httpProtocol = http
      .baseUrl("https://www.test.com")
      .inferHtmlResources()
      .acceptHeader("*/*")
      .acceptEncodingHeader("gzip, deflate")
      .acceptLanguageHeader("en-US,en;q=0.5")
      .userAgentHeader("Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:67.0) Gecko/20100101 Firefox/67.0")
  
    val homepage = exec(http("homepage")
      .get("/?customer_type=" + Random.shuffle(customer_types.toList).head.toString))
      .exec { session =&gt;
        println(session)
        session
      }
  
    val home_page_scenario = scenario("PDP").exec(homepage)
  
    setUp(
      home_page_scenario.inject(
        rampUsers(10) during (5 seconds),
      ).protocols(httpProtocol),
    )
  }
  </code></pre>
  
  <p>After running the test with one user, I get the following session values 
  with customer_type equals either P or B</p>
  
  <pre><code>Session(PDP,10,1565009885331,Map(gatling.http.cache.baseUrl -&gt; https://test.test.com, gatling.http.cache.dns -&gt; io.gatling.http.cache.DnsCacheSupport$$anon$1@13cea563, gatling.http.cache.contentCache -&gt; io.gatling.core.util.cache.Cache@1acc69e3, gatling.http.ssl.sslContexts -&gt; SslContexts(io.netty.handler.ssl.OpenSslClientContext@534581dd,None), gatling.http.referer -&gt; https://test.test.com/?customer_type=B, gatling.http.cookies -&gt; CookieJar(Map(CookieKey(customer_type,www.test.com,/) -&gt; StoredCookie(customer_type=B, path=/, secure,true,false,1565009892233), CookieKey(test_session,test.com328110,/) -&gt; StoredCookie(test_session=OS96ekJ4Nk0zRkJBak5obDdES0RZaW1Qb1hHS1U1VG5YcndGbmxKT1hrV3p4WVpCZElSUXJISVlZRlZtNjRmazd4QVlYTHhlWHFyUjJIU2VLZUh1Q083NjFmVlFVdzNLMmVwckh5Z0JuOWJLaW1ab2FIbU13Qnl0UVdZblFSOHlrVXJWYUZTQ3dYL1ZOV1dZM2Z0MWxGK1piN1lpbGdTRUdZeXBGQXllaHBPcW83eW0zTStuc1huelJOZzRPNkFBN2RKN281Y2FvSUU0V01BTVk5RmtWQT09LS1nbEMxV1FId3MvT0ZaVFBFV2YwVGZnPT0%3D--5a89e73be05416d96f3acf2e3f927495caf3d491, domain=.test,cin, path=/, secure, HTTPOnly,false,false,1565009892233), CookieKey(user_group,www.test.com,/) -&gt; StoredCookie(user_group=n, path=/,true,false,1565009892233)))),0,OK,List(),io.gatling.core.protocol.ProtocolComponentsRegistry$$Lambda$531/0x0000000840511040@6360231f)
  </code></pre>
  
  <p>After running it with the 10 users however, i get all the sessions with either P or B for customer type but it's the same for all users.</p>