Proxy URL for request

Add ProxyURL to Request
Add ProxyURL via context
Update example

_examples/proxy_switcher/proxy_switcher.go

@@ -21,6 +21,7 @@ func main() {
 
 	// Print the response
 	c.OnResponse(func(r *colly.Response) {
+		log.Printf("Proxy Address: %s\n", r.Request.ProxyURL)
 		log.Printf("%s\n", bytes.Replace(r.Body, []byte("\n"), nil, -1))
 	})
 

colly.go

@@ -158,6 +158,13 @@ type cookieJarSerializer struct {
 
 var collectorCounter uint32
 
+// The key type is unexported to prevent collisions with context keys defined in
+// other packages.
+type key int
+
+// ProxyURLKey is the context key for the request proxy address.
+const ProxyURLKey key = 0
+
 var (
 	// ErrForbiddenDomain is the error thrown if visiting
 	// a domain which is not allowed in AllowedDomains
@@ -587,6 +594,9 @@ func (c *Collector) fetch(u, method string, depth int, requestData io.Reader, ct
 		request.URL = req.URL
 		request.Headers = &req.Header
 	}
+	if proxyURL, ok := req.Context().Value(ProxyURLKey).(string); ok {
+		request.ProxyURL = proxyURL
+	}
 	atomic.AddUint32(&c.responseCount, 1)
 	response.Ctx = ctx
 	response.Request = request

proxy/proxy.go

@@ -15,6 +15,7 @@
 package proxy
 
 import (
+	"context"
 	"net/http"
 	"net/url"
 	"sync/atomic"
@@ -27,9 +28,11 @@ type roundRobinSwitcher struct {
 	index     uint32
 }
 
-func (r *roundRobinSwitcher) GetProxy(_ *http.Request) (*url.URL, error) {
+func (r *roundRobinSwitcher) GetProxy(pr *http.Request) (*url.URL, error) {
 	u := r.proxyURLs[r.index%uint32(len(r.proxyURLs))]
 	atomic.AddUint32(&r.index, 1)
+	ctx := context.WithValue(pr.Context(), colly.ProxyURLKey, u.String())
+	*pr = *pr.WithContext(ctx)
 	return u, nil
 }
 

request.go

@@ -48,6 +48,8 @@ type Request struct {
 	collector *Collector
 	abort     bool
 	baseURL   *url.URL
+	// ProxyURL is the proxy address that handles the request
+	ProxyURL string
 }
 
 type serializableRequest struct {