context.SendFile supports resume (by range). https://github.com/kataras/iris/issues/359#issuecomment-240471538

context.go

@@ -607,9 +607,10 @@ func (ctx *Context) Markdown(status int, markdown string) {
 }
 
 // ServeContent serves content, headers are autoset
-// receives three parameters, it's low-level function, instead you can use .ServeFile(string)
+// receives three parameters, it's low-level function, instead you can use .ServeFile(string,bool)/SendFile(string,string)
 //
 // You can define your own "Content-Type" header also, after this function call
+// Doesn't implements resuming (by range), use ctx.SendFile instead
 func (ctx *Context) ServeContent(content io.ReadSeeker, filename string, modtime time.Time, gzipCompression bool) error {
 	if t, err := time.Parse(config.TimeFormat, ctx.RequestHeader(ifModifiedSince)); err == nil && modtime.Before(t.Add(1*time.Second)) {
 		ctx.RequestCtx.Response.Header.Del(contentType)
@@ -644,7 +645,9 @@ func (ctx *Context) ServeContent(content io.ReadSeeker, filename string, modtime
 // gzipCompression (bool)
 //
 // You can define your own "Content-Type" header also, after this function call
-// This function doesn't implement resuming, use ctx.RequestCtx.SendFile/fasthttp.ServeFileUncompressed(ctx.RequestCtx,path)/ServeFile(ctx.RequestCtx,path) instead
+// This function doesn't implement resuming (by range), use ctx.SendFile/fasthttp.ServeFileUncompressed(ctx.RequestCtx,path)/fasthttpServeFile(ctx.RequestCtx,path) instead
+//
+// Use it when you want to serve css/js/... files to the client, for bigger files and 'force-download' use the SendFile
 func (ctx *Context) ServeFile(filename string, gzipCompression bool) error {
 	f, err := os.Open(filename)
 	if err != nil {
@@ -665,17 +668,10 @@ func (ctx *Context) ServeFile(filename string, gzipCompression bool) error {
 
 // SendFile sends file for force-download to the client
 //
-// You can define your own "Content-Type" header also, after this function call
-// for example: ctx.Response.Header.Set("Content-Type","thecontent/type")
-// This function doesn't implement resuming, use ctx.RequestCtx.SendFile instead
-func (ctx *Context) SendFile(filename string, destinationName string) error {
-	err := ctx.ServeFile(filename, false)
-	if err != nil {
-		return err
-	}
-
+// Use this instead of ServeFile to 'force-download' bigger files to the client
+func (ctx *Context) SendFile(filename string, destinationName string) {
+	ctx.RequestCtx.SendFile(filename)
 	ctx.RequestCtx.Response.Header.Set(contentDisposition, "attachment;filename="+destinationName)
-	return nil
 }
 
 // Stream same as StreamWriter

context/context.go

@@ -69,7 +69,7 @@ type (
 		XML(int, interface{}) error
 		ServeContent(io.ReadSeeker, string, time.Time, bool) error
 		ServeFile(string, bool) error
-		SendFile(string, string) error
+		SendFile(string, string)
 		Stream(func(*bufio.Writer))
 		StreamWriter(cb func(*bufio.Writer))
 		StreamReader(io.Reader, int)

plugin.go

@@ -248,7 +248,8 @@ func (p *pluginContainer) Add(plugins ...Plugin) error {
 		}
 		// Activate the plugin, if no error then add it to the plugins
 		if pluginObj, ok := plugin.(pluginActivate); ok {
-			tempPluginContainer := *p
+
+			tempPluginContainer := *p // contains the mutex but we' re safe here.
 			err := pluginObj.Activate(&tempPluginContainer)
 			if err != nil {
 				return errPluginActivate.Format(pName, err.Error())