add callback for pipe start and pipe err (#145)

* add onstart onerr cb

* cover by e2e

* add missing plugin

* happy lint

plugin/testplugin/main.go

@@ -0,0 +1,66 @@
+//go:build e2e
+
+package main
+
+import (
+	"net/rpc"
+
+	"github.com/tg123/sshpiper/libplugin"
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+
+	libplugin.CreateAndRunPluginTemplate(&libplugin.PluginTemplate{
+		Name:  "testplugin",
+		Usage: "e2e test plugin only",
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:     "rpcserver",
+				Required: true,
+			},
+			&cli.StringFlag{
+				Name:     "testsshserver",
+				Required: true,
+			},
+		},
+		CreateConfig: func(c *cli.Context) (*libplugin.SshPiperPluginConfig, error) {
+
+			rpcclient, err := rpc.DialHTTP("tcp", c.String("rpcserver"))
+			if err != nil {
+				return nil, err
+			}
+
+			host, port, err := libplugin.SplitHostPortForSSH(c.String("testsshserver"))
+			if err != nil {
+				return nil, err
+			}
+
+			return &libplugin.SshPiperPluginConfig{
+				NewConnectionCallback: func(conn libplugin.ConnMetadata) error {
+					return rpcclient.Call("TestPlugin.NewConnection", "", nil)
+				},
+				PipeStartCallback: func(conn libplugin.ConnMetadata) {
+					rpcclient.Call("TestPlugin.PipeStart", "", nil)
+				},
+				PipeErrorCallback: func(conn libplugin.ConnMetadata, err error) {
+					rpcclient.Call("TestPlugin.PipeError", err.Error(), nil)
+				},
+				PasswordCallback: func(conn libplugin.ConnMetadata, password []byte) (*libplugin.Upstream, error) {
+					var newpass string
+					err := rpcclient.Call("TestPlugin.Password", string(password), &newpass)
+					if err != nil {
+						return nil, err
+					}
+
+					return &libplugin.Upstream{
+						Host:          host,
+						Port:          int32(port),
+						Auth:          libplugin.CreatePasswordAuthFromString(newpass),
+						IgnoreHostKey: true,
+					}, nil
+				},
+			}, nil
+		},
+	})
+}