FCM API错误请求

Question

我正在尝试从Ruby on Rails项目通过FCM推送通知，这是我的代码：

require 'net/http'
require 'json'

def send_notifications
 log = Logger.new("log/notifications.log")
 begin
  uri = URI.parse("https://fcm.googleapis.com/fcm/send")
  http = Net::HTTP.new(uri.host, uri.port)

  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE

  key = '...'
  hash = {:notification => {:sound =>  "default", :title => "test", :text => "test", :badge => "0"}, :data => {:targetID => "1", :to => "..."}}

req = Net::HTTP::Post.new(uri.path, {'Content-Type' => 'application/json', 'Authorization' => "key=#{key}"})
req.body = hash.to_json
response = http.request(req)
log.debug("response #{response.body}")
rescue => e
  log.debug("failed #{e}")
 end
end

我收到Bad Request 400错误，并且调试响应正文仅显示以下内容：“至”

请帮助我调试此问题。谢谢