Do not set Content-Length in GET and HEAD requests according to pull request #31 (thanks to @buaazp )

http.go

@@ -717,11 +717,14 @@ func (req *Request) Write(w *bufio.Writer) error {
 		req.Header.SetMultipartFormBoundary(req.multipartFormBoundary)
 	}
 
-	req.Header.SetContentLength(len(body))
+	hasBody := !req.Header.noBody()
+	if hasBody {
+		req.Header.SetContentLength(len(body))
+	}
 	if err = req.Header.Write(w); err != nil {
 		return err
 	}
-	if !req.Header.noBody() {
+	if hasBody {
 		_, err = w.Write(body)
 	} else if len(body) > 0 {
 		return fmt.Errorf("Non-zero body for non-POST request. body=%q", body)

http_test.go

@@ -10,6 +10,25 @@ import (
 	"testing"
 )
 
+func TestRequestNoContentLength(t *testing.T) {
+	var r Request
+
+	r.Header.SetMethod("HEAD")
+	r.Header.SetHost("foobar")
+
+	s := r.String()
+	if strings.Contains(s, "Content-Length: ") {
+		t.Fatalf("unexpected content-length in HEAD request %q", s)
+	}
+
+	r.Header.SetMethod("POST")
+	fmt.Fprintf(r.BodyWriter(), "foobar body")
+	s = r.String()
+	if !strings.Contains(s, "Content-Length: ") {
+		t.Fatalf("missing content-length header in non-GET request %q", s)
+	}
+}
+
 func TestRequestReadGzippedBody(t *testing.T) {
 	var r Request