interfaces make for much slowness for some reason

api.go

 package main
 
 import (
-	"strings"
 	"bufio"
 	"encoding/binary"
 	"encoding/json"
@@ -11,7 +10,9 @@ import (
 	url_ "net/url"
 	"os"
 	"path/filepath"
+	"strings"
 	"syscall"
+	"time"
 
 	"github.com/pkg/sftp"
 	"golang.org/x/crypto/ssh"
@@ -19,11 +20,6 @@ import (
 	"github.com/pkg/errors"
 )
 
-var (
-	errBadCommand = errors.New("Invalid command")
-	errBadArgs    = errors.New("Invalid arguments")
-)
-
 // type yielded from binaryCommands or testCommands
 type command struct {
 	Name string            `json:"command"`
@@ -62,11 +58,11 @@ type mySFTPClient struct {
 	SFTP *sftp.Client
 }
 
-func (c mySFTPClient) Close() error {
+func (c *mySFTPClient) Close() error {
 	return c.SFTP.Close()
 }
 
-func (c mySFTPClient) Create(path string) (io.WriteCloser, error) {
+func (c *mySFTPClient) Create(path string) (io.WriteCloser, error) {
 	f, err := c.SFTP.Create(path)
 	if err != nil {
 		return sftpFile{}, err
@@ -74,26 +70,26 @@ func (c mySFTPClient) Create(path string) (io.WriteCloser, error) {
 	return sftpFile{f}, nil
 }
 
-func (c mySFTPClient) Poke() bool {
+func (c *mySFTPClient) Poke() bool {
 	_, err := c.SFTP.Getwd()
 	return err == nil
 }
 
-func (c mySFTPClient) Open(path string) (io.ReadCloser, error) {
+func (c *mySFTPClient) Open(path string) (io.ReadCloser, error) {
 	return c.SFTP.Open(path)
 }
 
-func (c mySFTPClient) ReadDir(path string) ([]os.FileInfo, error) {
+func (c *mySFTPClient) ReadDir(path string) ([]os.FileInfo, error) {
 	return c.SFTP.ReadDir(path)
 }
 
-func (c mySFTPClient) Remove(path string) error {
+func (c *mySFTPClient) Remove(path string) error {
 	return c.SFTP.Remove(path)
 }
 
 type sftpAPI struct {
 	URL    *url_.URL
-	Client sftpClient
+	Client *sftp.Client
 	Cfg    ssh.ClientConfig
 	Req    io.Reader
 	Resp   io.Writer
@@ -213,10 +209,13 @@ func (s sftpAPI) doPut(source, dest string) error {
 	}
 	defer fin.Close()
 
-	_, err = io.Copy(fout, fin)
+	t := time.Now()
+	n, err := io.Copy(fout, fin)
 	if err != nil {
 		return errors.Wrapf(err, "upload failed for %s -> %s", source, dest)
 	}
+	tt := time.Now().Sub(t).Seconds()
+	debug("%fs, %d bytes; throughput %f Mb/s", tt, n, float64(n)*8/1024/1024/tt)
 	return nil
 }
 
@@ -286,7 +285,7 @@ func (s sftpAPI) doDelete(path string) error {
 
 // make sure the client is connected by poking it
 func (s *sftpAPI) ensureConnected() error {
-	if !s.Client.Poke() {
+	if _, err := s.Client.Getwd(); err != nil {
 		debug("not connected, connecting")
 		return s.connect()
 	}
@@ -296,6 +295,7 @@ func (s *sftpAPI) ensureConnected() error {
 func (s sftpAPI) doCommand(cmd command) result {
 	zult := result{"ok", "", ""}
 
+	t := time.Now()
 	err := s.ensureConnected()
 	if err != nil {
 		zult.Status = "fail"
@@ -333,6 +333,8 @@ func (s sftpAPI) doCommand(cmd command) result {
 		zult.Status = "error"
 		zult.Message = fmt.Sprintf("unknown command: \"%s\"", cmd.Name)
 	}
+
+	debug("command took %fs", time.Now().Sub(t).Seconds())
 	return zult
 }
 
@@ -369,7 +371,7 @@ func (s *sftpAPI) connect() error {
 	if err != nil {
 		return err
 	}
-	s.Client = mySFTPClient{c}
+	s.Client = c
 	return nil
 }