Use tomb v2, update deps, fix hang on stale connection

- Use tomb v2 to properly spawn and reap goroutines (hopefully)
- Update deps
- Fix hang on stale connection due to improper goroutine management

vendor/golang.org/x/sys/unix/syscall_hurd.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build hurd
-// +build hurd
 
 package unix
 
@@ -12,6 +11,7 @@ package unix
 int ioctl(int, unsigned long int, uintptr_t);
 */
 import "C"
+import "unsafe"
 
 func ioctl(fd int, req uint, arg uintptr) (err error) {
 	r0, er := C.ioctl(C.int(fd), C.ulong(req), C.uintptr_t(arg))