fix detect the type of media message

go.mod

@@ -4,6 +4,7 @@ go 1.14
 
 require (
 	github.com/chai2010/webp v1.1.0
+	github.com/gabriel-vasile/mimetype v1.1.2
 	github.com/gorilla/websocket v1.4.2
 	github.com/kelaresg/go-skypeapi v0.1.2-0.20210220112556-a87881796d7b
 	github.com/lib/pq v1.7.0

go.sum

@@ -64,6 +64,8 @@ github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/gabriel-vasile/mimetype v1.1.2 h1:gaPnPcNor5aZSVCJVSGipcpbgMWiAAj9z182ocSGbHU=
+github.com/gabriel-vasile/mimetype v1.1.2/go.mod h1:6CDPel/o/3/s4+bp6kIbsWATq8pmgOisOPG40CJa6To=
 github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeMEF04=
 github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-kit/kit v0.8.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=

portal.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"github.com/gabriel-vasile/mimetype"
 	"maunium.net/go/mautrix/patch"
 
 	"encoding/hex"
@@ -1622,8 +1623,7 @@ func (portal *Portal) HandleMediaMessageSkype(source *User, download func(conn *
 	}
 
 	// synapse doesn't handle webp well, so we convert it. This can be dropped once https://github.com/matrix-org/synapse/issues/4382 is fixed
-	mimeType := http.DetectContentType(data)
-	//length := len(data)
+	mimeType := mimetype.Detect(data).String()
 	if mimeType == "image/webp" {
 		img, err := decodeWebp(bytes.NewReader(data))
 		if err != nil {