Don't depend on fuseshim for unmounting.

unmount.go

@@ -14,10 +14,8 @@
 
 package fuse
 
-import "github.com/jacobsa/fuse/internal/fuseshim"
-
 // Attempt to unmount the file system whose mount point is the supplied
 // directory.
 func Unmount(dir string) error {
-	return fuseshim.Unmount(dir)
+	return unmount(dir)
 }

unmount_linux.go

@@ -0,0 +1,23 @@
+package fuseshim
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+)
+
+func unmount(dir string) (err error) {
+	// Call fusermount.
+	cmd := exec.Command("fusermount", "-u", dir)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		if len(output) > 0 {
+			output = bytes.TrimRight(output, "\n")
+			err = fmt.Errorf("%v: %s", err, output)
+		}
+
+		return
+	}
+
+	return
+}

unmount_std.go

@@ -0,0 +1,18 @@
+// +build !linux
+
+package fuse
+
+import (
+	"os"
+	"syscall"
+)
+
+func unmount(dir string) (err error) {
+	err = syscall.Unmount(dir, 0)
+	if err != nil {
+		err = &os.PathError{Op: "unmount", Path: dir, Err: err}
+		return
+	}
+
+	return
+}