Zabbix Agent 2 在尝试根据官方说明处理测试插件时抛出错误

package main
       
       import (
           "fmt"
           "io/ioutil"
           "net/http"
           "git.zabbix.com/ap/plugin-support/plugin/container"
           "git.zabbix.com/ap/plugin-support/plugin"
       )
       
       // Plugin must define structure and embed plugin.Base structure.
       type Plugin struct {
           plugin.Base
       }
       
       // Create a new instance of the defined plugin structure
       var impl Plugin
       
       // Plugin must implement one or several plugin interfaces.
       func (p *Plugin) Export(key string, params []string, ctx plugin.ContextProvider) (result interface{}, err error) {
           // You may use one of Critf, Errf, Infof, Warningf, Debugf, Tracef functions for logging.
           p.Infof("received request to handle %s key with %d parameters", key, len(params))
       
           // Fetch response from the specified URL, it should be just the IP address.
           resp, err := http.Get("https://api.ipify.org")
           if err != nil {
               // Plugin will return an error response if the request failed
               return nil, err
           }
       
           defer resp.Body.Close()
       
           body, err := ioutil.ReadAll(resp.Body)
           if err != nil {
               // Plugin will return an error response if it failed to read the response
               return nil, err
           }
       
           return string(body), nil
       }
       
       func init() {
           // Register our metric, specifying the plugin and metric details.
           // 1 - a pointer to plugin implementation
           // 2 - plugin name
           // 3 - metric name (item key)
           // 4 - metric description
           //
           // NB! The metric description must end with a period, otherwise the Zabbix agent 2 will return an error and won't start!
           // Metric name (item key) and metric description can be repeated in a loop to register additional metrics.
           plugin.RegisterMetrics(&impl, "Myip", "myip", "Return the external IP address of the host where agent is running.")
       }
       
       // This is the main function, it is required to compile the plugin.
       // By default the function implements our packages to handle the plugin creation and execution.
       func main() {
           h, err := container.NewHandler(impl.Name())
           if err != nil {
               panic(fmt.Sprintf("failed to create plugin handler %s", err.Error()))
           }
           impl.Logger = &h
       
           err = h.Execute()
           if err != nil {
               panic(fmt.Sprintf("failed to execute plugin handler %s", err.Error()))
           }
       }