support static sources in paths with regular expressions (#824) (#2799)

This allows to proxy requests to other servers by using regular
expressions.

internal/staticsources/hls/source.go

@@ -20,8 +20,9 @@ import (
 
 // Source is a HLS static source.
 type Source struct {
-	ReadTimeout conf.StringDuration
-	Parent      defs.StaticSourceParent
+	ResolvedSource string
+	ReadTimeout    conf.StringDuration
+	Parent         defs.StaticSourceParent
 }
 
 // Log implements logger.Writer.
@@ -43,7 +44,7 @@ func (s *Source) Run(params defs.StaticSourceRunParams) error {
 
 	var c *gohlslib.Client
 	c = &gohlslib.Client{
-		URI: params.Conf.Source,
+		URI: s.ResolvedSource,
 		HTTPClient: &http.Client{
 			Timeout: time.Duration(s.ReadTimeout),
 			Transport: &http.Transport{