Merge Fields not Working about mailgun-ruby HOT 11 CLOSED

http_client = RestClient::Resource.new("https://api.mailgun.net/v2",
                :user       => "api",
                :password   => "[MAILGUN KEY]",
                :user_agent => "mailgun-sdk-ruby/1.0.2")

data = {"from"                 => ["[email protected]"],
        "subject"              => ["Merge Fields Test"],
        "text"                 => ["Hello %recipient.first%, this is a test. Your full name is %recipient.first% %last%."],
        "to"                   => ["'John Doe' <[email protected]>", "'Jane Doe' <[email protected]>"],
        "recipient-variables"  => [ {"[email protected]" => {"id" => nil},
                                     "[email protected]" => {"first" => "John", "last" => "Doe"},
                                     "[email protected]" => {"first" => "Jane", "last" => "Doe"}
                                  ]
        }

response = http_client["mail.domain.com/messages"].post(data)

http_client = RestClient::Resource.new("https://api.mailgun.net/v2",
               :user       => "api",
               :password   => "[MAILGUN KEY]",
               :user_agent => "mailgun-sdk-ruby/1.0.2")

data = {"from"                 => ["[email protected]"],
        "subject"              => ["Merge Fields Test"],
        "text"                 => ["Hello %recipient.first%, this is a test. Your full name is %recipient.first% %last%."],
        "to"                   => ["'John Doe' <[email protected]>", "'Jane Doe' <[email protected]>"],
        "recipient-variables"  =>  {"[email protected]" => {"id" => nil},
                                     "[email protected]" => {"first" => "John", "last" => "Doe"},
                                     "[email protected]" => {"first" => "Jane", "last" => "Doe"}
                                   }.to_json

        }

response = http_client["mail.domain.com/messages"].post(data)

...
def send_message(message)
  simple_setter("recipient-variables", JSON.generate(@recipient_variables))

  if @message.has_key?("recipient-variables")
    @message["recipient-variables"] = @message["recipient-variables"].first
  end

  response = @client.send_message(@domain, @message).to_h!
  message_id = response['id'].gsub(/\>|\</, '')
  @message_ids[message_id] = count_recipients()
  reset_message()
end
...