Pasted the implementation from bazilfuse.

mount_darwin.go

+package fuseshim
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+// OS X appears to cap the size of writes to 1 MiB. This constant is also used
+// for sizing receive buffers, so make it as small as it can be without
+// limiting write sizes.
+const maxWrite = 1 << 20
+
+var errNoAvail = errors.New("no available fuse devices")
+
+var errNotLoaded = errors.New("osxfusefs is not loaded")
+
+func loadOSXFUSE() error {
+	cmd := exec.Command("/Library/Filesystems/osxfusefs.fs/Support/load_osxfusefs")
+	cmd.Dir = "/"
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err := cmd.Run()
+	return err
+}
+
+func openOSXFUSEDev() (*os.File, error) {
+	var f *os.File
+	var err error
+	for i := uint64(0); ; i++ {
+		path := "/dev/osxfuse" + strconv.FormatUint(i, 10)
+		f, err = os.OpenFile(path, os.O_RDWR, 0000)
+		if os.IsNotExist(err) {
+			if i == 0 {
+				// not even the first device was found -> fuse is not loaded
+				return nil, errNotLoaded
+			}
+
+			// we've run out of kernel-provided devices
+			return nil, errNoAvail
+		}
+
+		if err2, ok := err.(*os.PathError); ok && err2.Err == syscall.EBUSY {
+			// try the next one
+			continue
+		}
+
+		if err != nil {
+			return nil, err
+		}
+		return f, nil
+	}
+}
+
+func callMount(dir string, conf *mountConfig, f *os.File, ready chan<- struct{}, errp *error) error {
+	bin := "/Library/Filesystems/osxfusefs.fs/Support/mount_osxfusefs"
+
+	for k, v := range conf.options {
+		if strings.Contains(k, ",") || strings.Contains(v, ",") {
+			// Silly limitation but the mount helper does not
+			// understand any escaping. See TestMountOptionCommaError.
+			return fmt.Errorf("mount options cannot contain commas on darwin: %q=%q", k, v)
+		}
+	}
+	cmd := exec.Command(
+		bin,
+		"-o", conf.getOptions(),
+		// Tell osxfuse-kext how large our buffer is. It must split
+		// writes larger than this into multiple writes.
+		//
+		// OSXFUSE seems to ignore InitResponse.MaxWrite, and uses
+		// this instead.
+		"-o", "iosize="+strconv.FormatUint(maxWrite, 10),
+		// refers to fd passed in cmd.ExtraFiles
+		"3",
+		dir,
+	)
+	cmd.ExtraFiles = []*os.File{f}
+	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_CALL_BY_LIB=")
+	// TODO this is used for fs typenames etc, let app influence it
+	cmd.Env = append(cmd.Env, "MOUNT_FUSEFS_DAEMON_PATH="+bin)
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+
+	err := cmd.Start()
+	if err != nil {
+		return err
+	}
+	go func() {
+		err := cmd.Wait()
+		if err != nil {
+			if buf.Len() > 0 {
+				output := buf.Bytes()
+				output = bytes.TrimRight(output, "\n")
+				msg := err.Error() + ": " + string(output)
+				err = errors.New(msg)
+			}
+		}
+		*errp = err
+		close(ready)
+	}()
+	return err
+}
+
+func mount(dir string, conf *mountConfig, ready chan<- struct{}, errp *error) (*os.File, error) {
+	f, err := openOSXFUSEDev()
+	if err == errNotLoaded {
+		err = loadOSXFUSE()
+		if err != nil {
+			return nil, err
+		}
+		// try again
+		f, err = openOSXFUSEDev()
+	}
+	if err != nil {
+		return nil, err
+	}
+	err = callMount(dir, conf, f, ready, errp)
+	if err != nil {
+		f.Close()
+		return nil, err
+	}
+	return f, nil
+}