It took me a while to figure out how to run a sudo command (which requires an interactive console, in my case) with Go's SSH package. This is what I found.

config.go

package main

const (
	sshKey   string = "/Users/myuser/.ssh/id_rsa_mykey"
	hostname string = "myhost.com"
)

main.go

package main

import (
	"io/ioutil"
	"log"
	"os"

	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/terminal"
)

func main() {
	key, err := ioutil.ReadFile(sshKey)
	if err != nil {
		panic(err)
	}
	signer, err := ssh.ParsePrivateKey(key)
	if err != nil {
		panic(err)
	}
	authMethod := ssh.PublicKeys(signer)

	config := &ssh.ClientConfig{
		User: os.Getenv("LOGNAME"),
		Auth: []ssh.AuthMethod{
			authMethod,
		},
	}

	conn, err := ssh.Dial("tcp", hostname+":22", config)
	if err != nil {
		panic(err)
	}
	session, err := conn.NewSession()
	if err != nil {
		panic(err)
	}
	defer session.Close()

	modes := ssh.TerminalModes{
		ssh.ECHO:          0,
		ssh.TTY_OP_ISPEED: 14400,
		ssh.TTY_OP_OSPEED: 14400,
	}

	if err := session.RequestPty("xterm", 80, 40, modes); err != nil {
		log.Fatalf("request for pseudo terminal failed: %s", err)
	}

	session.Stdout = os.Stdout
	session.Stderr = os.Stderr

	session.Stdin = os.Stdin
	terminal.MakeRaw(0)
	session.Run("sudo touch hi")

	log.Println("Done")
}