feat: make connection method using system 'ssh' the default (add ssh+go:// fallback)

internal/cli/config/connection.go

@@ -12,8 +12,12 @@ import (
 )
 
 type MachineConnection struct {
-	SSH        SSHDestination `yaml:"ssh,omitempty"`
-	SSHCLI     SSHDestination `yaml:"ssh_cli,omitempty"`
+	// SSH uses the system ssh CLI command to connect. This is the default SSH connection method.
+	SSH SSHDestination `yaml:"ssh,omitempty"`
+	// SSHCLI is a backward-compatible alias for SSH.
+	SSHCLI SSHDestination `yaml:"ssh_cli,omitempty"`
+	// SSHGo uses Go's built-in SSH library to connect.
+	SSHGo      SSHDestination `yaml:"ssh_go,omitempty"`
 	SSHKeyFile string         `yaml:"ssh_key_file,omitempty"`
 	// TCP is the address and port of the machine's API server.
 	// The pointer is used to omit the field when not set. Otherwise, yaml marshalling includes an empty object.
@@ -29,7 +33,9 @@ func (c *MachineConnection) String() string {
 	if c.SSH != "" {
 		return "ssh://" + string(c.SSH)
 	} else if c.SSHCLI != "" {
-		return "ssh+cli://" + string(c.SSHCLI)
+		return "ssh://" + string(c.SSHCLI)
+	} else if c.SSHGo != "" {
+		return "ssh+go://" + string(c.SSHGo)
 	} else if c.TCP != nil && c.TCP.IsValid() {
 		return fmt.Sprintf("tcp://%s", c.TCP)
 	} else if c.Unix != "" {
@@ -46,6 +52,9 @@ func (c *MachineConnection) Validate() error {
 	if c.SSHCLI != "" {
 		setCount++
 	}
+	if c.SSHGo != "" {
+		setCount++
+	}
 	if c.TCP != nil && c.TCP.IsValid() {
 		setCount++
 	}
@@ -54,10 +63,10 @@ func (c *MachineConnection) Validate() error {
 	}
 
 	if setCount == 0 {
-		return errors.New("no connection method specified (ssh, ssh_cli, tcp, or unix required)")
+		return errors.New("no connection method specified (ssh, ssh_go, tcp, or unix required)")
 	}
 	if setCount > 1 {
-		return errors.New("only one connection method allowed per connection (ssh, ssh_cli, tcp, or unix)")
+		return errors.New("only one connection method allowed per connection (ssh, ssh_go, tcp, or unix)")
 	}
 
 	return nil

internal/cli/config/connection_test.go

@@ -30,18 +30,32 @@ func TestMachineConnection_String(t *testing.T) {
 			want: "ssh://user@host.com:2222",
 		},
 		{
-			name: "ssh_cli connection",
+			name: "ssh_cli connection (backward compat alias for ssh)",
 			conn: MachineConnection{
 				SSHCLI: "user@host.com",
 			},
-			want: "ssh+cli://user@host.com",
+			want: "ssh://user@host.com",
 		},
 		{
-			name: "ssh_cli connection with port",
+			name: "ssh_cli connection with port (backward compat alias for ssh)",
 			conn: MachineConnection{
 				SSHCLI: "user@host.com:2222",
 			},
-			want: "ssh+cli://user@host.com:2222",
+			want: "ssh://user@host.com:2222",
+		},
+		{
+			name: "ssh_go connection",
+			conn: MachineConnection{
+				SSHGo: "user@host.com",
+			},
+			want: "ssh+go://user@host.com",
+		},
+		{
+			name: "ssh_go connection with port",
+			conn: MachineConnection{
+				SSHGo: "user@host.com:2222",
+			},
+			want: "ssh+go://user@host.com:2222",
 		},
 		{
 			name: "tcp connection",
@@ -103,12 +117,19 @@ func TestMachineConnection_Validate(t *testing.T) {
 			wantErr: false,
 		},
 		{
-			name: "ssh_cli only - valid",
+			name: "ssh_cli only - valid (backward compat)",
 			conn: MachineConnection{
 				SSHCLI: "user@host",
 			},
 			wantErr: false,
 		},
+		{
+			name: "ssh_go only - valid",
+			conn: MachineConnection{
+				SSHGo: "user@host",
+			},
+			wantErr: false,
+		},
 		{
 			name: "tcp only - valid",
 			conn: MachineConnection{
@@ -141,6 +162,15 @@ func TestMachineConnection_Validate(t *testing.T) {
 			wantErr: true,
 			errMsg:  "only one connection method allowed",
 		},
+		{
+			name: "ssh and ssh_go - error",
+			conn: MachineConnection{
+				SSH:   "user@host",
+				SSHGo: "user@host",
+			},
+			wantErr: true,
+			errMsg:  "only one connection method allowed",
+		},
 		{
 			name: "ssh and unix - error",
 			conn: MachineConnection{