Implement command-based echo app and HTTP handler

echo_app.go

@@ -0,0 +1,30 @@
+package ussher
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+
+	"golang.org/x/crypto/ssh"
+)
+
+type echoHandler struct {
+	count int
+}
+
+func (e *echoHandler) HandleExec(conn *ssh.ServerConn, channel ssh.Channel) {
+	e.count += 1
+	io.Copy(channel, channel)
+}
+
+func (e *echoHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	msg := fmt.Sprintf("Hello Echo World! Calls: %d", e.count)
+	w.Write([]byte(msg))
+}
+
+func RegisterEchoApp(conf *Config) error {
+	e := &echoHandler{}
+	conf.SSHApps["echo"] = e
+	conf.HTTPMux.Handle("/echo/", e)
+	return nil
+}