Remove examples/internal

Users find it frustrating that example code doesn't work out of tree.
This makes copying the examples out of the repo easier.

Relates to #1981

examples/play-from-disk/main.go

@@ -8,15 +8,18 @@
 package main
 
 import (
+	"bufio"
 	"context"
+	"encoding/base64"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/pion/webrtc/v4"
-	"github.com/pion/webrtc/v4/examples/internal/signal"
 	"github.com/pion/webrtc/v4/pkg/media"
 	"github.com/pion/webrtc/v4/pkg/media/ivfreader"
 	"github.com/pion/webrtc/v4/pkg/media/oggreader"
@@ -248,7 +251,7 @@ func main() {
 
 	// Wait for the offer to be pasted
 	offer := webrtc.SessionDescription{}
-	signal.Decode(signal.MustReadStdin(), &offer)
+	decode(readUntilNewline(), &offer)
 
 	// Set the remote SessionDescription
 	if err = peerConnection.SetRemoteDescription(offer); err != nil {
@@ -275,8 +278,52 @@ func main() {
 	<-gatherComplete
 
 	// Output the answer in base64 so we can paste it in browser
-	fmt.Println(signal.Encode(*peerConnection.LocalDescription()))
+	fmt.Println(encode(peerConnection.LocalDescription()))
 
 	// Block forever
 	select {}
 }
+
+// Read from stdin until we get a newline
+func readUntilNewline() string {
+	var err error
+	var in string
+
+	r := bufio.NewReader(os.Stdin)
+	for {
+		in, err = r.ReadString('\n')
+		if err != nil && !errors.Is(err, io.EOF) {
+			panic(err)
+		}
+
+		if in = strings.TrimSpace(in); len(in) > 0 {
+			break
+		}
+	}
+
+	fmt.Println("")
+
+	return in
+}
+
+// JSON encode + base64 a SessionDescription
+func encode(obj *webrtc.SessionDescription) string {
+	b, err := json.Marshal(obj)
+	if err != nil {
+		panic(err)
+	}
+
+	return base64.StdEncoding.EncodeToString(b)
+}
+
+// Decode a base64 and unmarshal JSON into a SessionDescription
+func decode(in string, obj *webrtc.SessionDescription) {
+	b, err := base64.StdEncoding.DecodeString(in)
+	if err != nil {
+		panic(err)
+	}
+
+	if err = json.Unmarshal(b, obj); err != nil {
+		panic(err)
+	}
+}