Fix http_proxy variable name in http_response plugin

plugins/inputs/http_response/README.md

@@ -10,6 +10,9 @@ This input plugin checks HTTP/HTTPS connections.
   ## Server address (default http://localhost)
   # address = "http://localhost"
 
+  ## Set http_proxy (telegraf uses the system wide proxy settings if it's is not set)
+  # http_proxy = "http://localhost:8888"
+
   ## Set response_timeout (default 5 seconds)
   # response_timeout = "5s"
 

plugins/inputs/http_response/http_response.go

@@ -22,7 +22,7 @@ import (
 // HTTPResponse struct
 type HTTPResponse struct {
 	Address             string
-	Proxy               string
+	HTTPProxy           string `toml:"http_proxy"`
 	Body                string
 	Method              string
 	ResponseTimeout     internal.Duration
@@ -120,7 +120,7 @@ func (h *HTTPResponse) createHttpClient() (*http.Client, error) {
 	}
 	client := &http.Client{
 		Transport: &http.Transport{
-			Proxy:             getProxyFunc(h.Proxy),
+			Proxy:             getProxyFunc(h.HTTPProxy),
 			DisableKeepAlives: true,
 			TLSClientConfig:   tlsCfg,
 		},